Cardiac Catheterization in Congenital Heart Disease: Pediatric and Adult - Part 7 ppt

This vessel must be long enough to allow the very distal placement of the tip of the supporting guide wire and of a large enough diameter to accommodate the distal end of the fully inflat

Encore™ indeflator device

The Encore™ device (Medi-Tech, Boston Scientific, Natick,

MA) has a clear polycarbonate syringe barrel encased in a

covering that holds an analog manometer The

manome-ter is attached to the syringe lumen and has a maximum

pressure of 26 atms The syringe has a capacity of 20 ml

The ratchet mechanism on the syringe plunger is engaged

all of the time unless deliberately released by compressing

a squeeze/release button on the side of the barrel

B Braun™ angioplasty inflation device

The B Braun™ angioplasty inflation device (B Braun

Medical Inc., Bethlehem, PA) has a 25 ml clear

polycar-bonate syringe barrel with an analog pressure gauge,

which reaches and holds 30 atms pressure The syringe

has a rapid action “winged” locking mechanism, which

locks very quickly, adjusts very accurately and holds at

high pressures

Merit Medical™ inflation devices

Merit Medical (Merit Medical Systems, Salt Lake City, UT)

has four different inflation devices, all with a clear 20 ml

polycarbonate barrel The syringe has a squeeze “bar”

on a “T” handle to release the ratchet mechanism The

difference in the four inflation devices is in the type

of manometer gauge All of the gauges are electronic, but

are available in analog or digital and in local or remote

configurations and with, or without, built in timers

Bard Max 30™ inflation device

The Max 30™ (C.R Bard, Inc., Covington, GA) has a “T”

shaped handle over the polycarbonate barrel of a 20 ml

capacity syringe A lever which moves from side to side

across the “T” locks or releases the ratchet mechanism

of the syringe The Max 30™ inflation devices can deliver

30 atmospheres of pressure

The only additional criterion for the use of any of these

inflation devices is that the operator must be very familiar

with the operation of the specific device that is being used

Technique for the implant of intravascular

stents

The technique for the delivery and implant of the J & J™,

Palmaz™ stents (Johnson & Johnson, Warren, NJ) has

been developed and modified extensively during the

fifteen years of the clinical use of these stents in congenital

and pediatric cardiac patients Unfortunately, the stent

and balloon technology for this “non-approved” use has

not kept pace adequately with the complex congenitallesions for which stent therapy now is routinely utilized.Relative to the developments in stents and stent tech-niques for coronary arteries, the stents and deliveryequipment for congenital lesions are a decade behind indevelopment and in their introduction for clinical use inthe United States There have been some improvements

in the stents which are approved for use in adult eral vascular disease and which have filtered down to thepediatric/congenital population At the same time, thechanges/improvements in the delivery/implant tech-niques for congenital heart patients were developed pre-dominately in pediatric/congenital catheterization labor-atories during the decade and a half of the use of stents

periph-in these patients

All “self-mounted” or “hand-mounted” stents are rently delivered through or with the use of a long sheathadvanced to and past the lesion where the stent is to beimplanted To date, there are no satisfactory ways ofhand-mounting stents and securing them tightly enough

cur-on the ballocur-ons to allow ccur-onfident and safe delivery of a

stent without the use of a long sheath Even if secured tothe balloon, without the use of a long sheath, the stiff,sharp exposed ends of a rigid stent that is hand-mounted

on a balloon, easily extend off the balloon, catch on travascular structures, and are displaced off the balloonduring its passage through the vascular channels to thelesion If the stent catches on structures as the stent/balloon is being advanced, the stent is displaced prox-imally on the balloon catheter This prevents delivery tothe lesion and creates a problem in getting the stent out

in-of the vessel and body, but usually does not result in anerrant, free-floating stent If the stent catches on structuresduring the withdrawal of the balloon/stent/catheter, thestent is displaced onto the wire distal to the balloon.Without sophisticated and difficult retrieval techniques,this results in a stent potentially free floating in the circula-tion! At present, a long-sheath technique is recommendedand is always used for the delivery of hand-mountedstents

The equipment and techniques for the delivery of all

of the available large diameter, hand-mounted stents tothe proximal pulmonary arteries, to the central systemicveins, and to the large systemic arteries are almost ident-ical, although the delivery to the pulmonary arteries isusually more complex and difficult The similarities in theequipment, and the general techniques for the deliveryand implant used for all of the stents currently availablefor the larger vessels are described in this chapter Thedelivery and implant of the rigid Palmaz™ P _ _ 8 and

P _ _ 10 stents are the most difficult and dangerous.Familiarity with the techniques for delivering those stentsshould make the delivery of most other stents relativelystraightforward The availability of pre-mounted large

stents on appropriate sized balloons may change these

techniques dramatically within the next few years

The peculiarities and particular difficulties with the

delivery of stents to specific locations in specific vessels

are discussed in Chapters 23, 24 and 25, which cover the

use of intravascular stents in pulmonary arteries, systemic

veins and systemic arteries, respectively Peculiarities in

the general delivery of the newer, more recently available

stents are discussed at the end of this section on technique

General technique for stent delivery

Most intravascular stent implants in congenital heart

patients can be performed with well controlled, deep

sedation and liberal local anesthesia However, since the

procedures can be very long, which becomes

uncomfort-able for the patient, general anesthesia often is used

elect-ively General anesthesia becomes essential when the

implant of a stent or even part of the procedure is

per-formed from the neck, when it is known that the

proced-ure definitely will be of a very long duration, or when

the patient needs endotracheal intubation for some other

reason General anesthesia has the advantage of another

physician besides the catheterizing physician monitoring

the patient and having some responsibility for the patient’s

degree of sedation and the control of the patient’s airway

With the use of either sedation alone, or when general

anesthesia is used, the patient requires a secure

intra-venous line for the administration of supplemental

seda-tion and other medicaseda-tions during the procedure Often,

just before the actual expansion of the stent for implant and

even though the patient appears sound asleep, the patient

is given a supplemental dose of sedation/anesthesia in

order to ensure that the patient remains absolutely still at

the moment of implant

All patients undergoing stent implant have an

indwelling arterial line in place during the entire

proced-ure This line allows instantaneous and continuous

moni-toring of systemic blood pressure and the obtaining of

necessary blood gases throughout the procedure It

al-ways is better to anticipate and, in turn, to prevent

prob-lems with the patient than to try to compensate for a

catastrophe once it has occurred A subtle change in the

continuously displayed intravascular blood pressure

which is on a monitor provides an early indicator of

impending trouble, while the periodically displayed

pres-sure from a “cycling” arm blood prespres-sure cuff recorder

may well appear long after the adverse event begins

Every patient undergoing a stent implant has an

indwelling bladder catheter (Foley™) placed at the

begin-ning of the procedure No amount of sedation or analgesia

compensates for the discomfort of an over-distended

uri-nary bladder during a long procedureaparticularly if it is

unexpectedly long!

In a patient undergoing stent implant in the pulmonary

arteries or systemic venous systems, one extra venous

catheter is introduced into the venous system in addition to

the venous line(s) which will be necessary for the delivery

of the stent(s), in order to have an extra catheter in the venous system in addition to the number of catheters

through which stents will be delivered Thus, in a patient

in whom two stents are to be implanted simultaneously,

three venous catheters are introduced A separate line is

used for each individual stent delivery, while the additional

venous line is used to perform precise selective angiograms

pre, during, and immediately after the expansion of andimplant of the stent The additional, angiographic catheter

is positioned in the same vessel, close in proximity andproximally in the flow of blood to the stenosis/stentimplant area

Some operators advocate performing the “placement”angiograms during the stent implant through the longdelivery sheath after the sheath has been withdrawn offthe stent/balloon combination and back into the moreproximal vessel This technique is of no use during thepositioning of the stent/balloon combination before it

is completely out of the delivery sheath (and no longerretrievable) Often the details of the anatomy from

angiograms with injections through the sheath are not

suitable The shaft of the balloon catheter fills and promises most of the lumen of the sheath and the pressure

com-of the injection through the side port com-of the sheath is limited by the loose “seal” of the back-bleed valve of thesheath over the shaft of the catheter As a consequence, asufficient amount of contrast cannot be delivered rapidlyenough with a high enough pressure to visualize the

stenosis–stent relationships accurately.

In addition, in order to perform the angiogram throughthe sheath during the stent implant, the sheath must be

withdrawn completely off the balloon and not just off the

stent Once the sheath is completely off the balloon/stent,further readjustment of the stent/balloon position is moredifficult In addition, this places the distal tip of the sheath

very proximal to both the stent and the area of stenosis in

the vessel As the contrast is injected relatively slowlythrough the sheath and into the more proximal vessel, thecontrast is diluted by adjacent, rapidly flowing blood, pre-

venting an adequate visualization of the area of interest.

Also when the sheath tip is far proximal to the area ofstenosis, the tip is often proximal to a bifurcation or a largebranching vessel, in which case, the majority of the smallquantity of slowly injected contrast is diverted into thebranch vessel and away from the stenotic area Poorangiographic imaging is more “the rule” than the excep-tion with the “through-the-sheath” technique and, as aconsequence, this technique is not recommended Inad-equate angiograms compromise the precise positioning

of the balloon/stent

The implant of stents into smaller, more peripheral

veins is the one exception where through-the-sheath

angiograms can be useful In this circumstance the vessel

is small, the sheath is “upstream” in the flow of blood, the

blood (and contrast) flow is slow and the injection is into a

very confined channel that is being stented Occasionally,

however, when the implant of a venous stent is

“retro-grade” in the vein (e.g a stent delivered into a femoral

vein from the jugular approach) the end of the sheath is

“downstream” in the flow from the lesion, with the result

that the contrast injected through the sheath flows away

from the lesion/stent and is of no value

The area(s) to be stented is(are) identified and

quantit-ated both hemodynamically from the pressure

measure-ments and angiographically with selective angiograms

into the precise vessel/area to be stented The techniques for

accurate, quantitative measurement are described in detail

in Chapter 11 and definitely should be adhered to for the

implant of intravascular stents After identifying and

measuring the stenosed area(s) of the involved vessel(s)

very accurately, an end-hole catheter is advanced from the

access site, across and well beyond the area of obstruction It

is extremely important that the vessel that is entered distal

to the obstruction is of a large diameter and is the longest

distal branch or tributary beyond the stenosis This vessel

must be long enough to allow the very distal placement of

the tip of the supporting guide wire and of a large enough

diameter to accommodate the distal end of the fully inflated

balloon which will be used to deliver and implant the

stent When the balloon and stent are centered on the

stenotic lesion during the stent expansion, the distal end

of the implanting balloon will always extend well beyond

the lesion and into the distal vessel Considerable extra time

is often required to enter this largest, distal vessel The

extra time spent in locating and achieving a good position

in this largest vessel with the end-hole catheter is essential

Once the catheter has been manipulated far into the

largest distal vessel, it is replaced with a Super Stiff™

exchange length guide wire If a long “floppy-tipped”

Super Stiff™ wire is used, the vessel must be very long

(and large enough in diameter) to accommodate the entire

curled up (“balled-up”) long floppy portion of the wire It

is imperative that the entire, long floppy tip, along with the

transition zone of the wire and a significant portion of the

extra stiff portion of the wire all extend a significant

dis-tance beyond the lesion The balloon and stent are

sup-ported only by the very stiff portion of the wire and by a

wire that is in a very secure distal position without the

capability of any to-and-fro movement The precise wire

position contributes significantly to the ultimate success

and safety of the procedure All the extra time required in

positioning the wire securely and very distally adds to the

likely success of the procedure, while any compromised

location of the wire is inviting a catastrophe

Over-dilation and tearing of a smaller branch vesselthat is just distal to the stenosis, is one of the greatest haz-ards during the implant of intravascular stents It usually

is a consequence of the wire and tip of the balloon beingmalpositioned prior to the stent implant When the bal-loon tip is positioned and fixed in, and then inflated in, anerroneous and unusually small vessel that is just distal tothe lesion, either it will rupture the vessel or the balloonwill be “milked” back out of the vessel during the inflationand, in turn, the stent will be displaced proximally

When there is a question about the size and tion of the particular anatomy in the area of the stenosisand, in particular, a question about the adequacy of thevessel distal to the stenosis, the anatomy is defined pre-

configura-cisely with a low-pressure, “sizing” balloon This is not

a pre-dilation of the area but rather, a “zero-pressure”

inflation with a very low-pressure sizing balloon in the area to determine the contour of the entire area! The most

satisfactory balloon for this sizing is the NuMED™ pressure “angioplasty” (“sizing”) balloon (NuMED Inc.,Hopkinton, NY), although any angioplasty type ballooncan be used for the sizing if it is inflated only at very lowpressure The sizing balloon is advanced over the pre-positioned stiff guide wire and positioned exactly in thearea of stenosis where the balloon/stent is to be inflated

low-The sizing balloon is inflated at a very low (zero!) pressure The balloon at this “zero” inflation pressure fills, and con-

forms to, the exact anatomy of the stenosis and vessel(s)

both proximal and distal to the lesion without dilating thearea at all This technique is useful particularly to deter-mine if there is sufficient diameter distal to the stenosis toaccommodate the distal tip of the balloon during inflation

of the balloon for the stent implant If the vessel distally

is too small, the zero pressure “sizing” balloon either does not inflate in the area or it gently “milks” back out

of the vessel The only disadvantage of this particular low-pressure sizing balloon is that it requires a 9-Frenchintroductory sheath, but at least this size will usually berequired for the delivery of the stent

As long as the stenosis is more than 3 to 4 mm in meter, pre-dilation of stenotic lesions before implanting a

dia-stent is not performed Only very tight stenoses, which are

too tight to allow a large, long delivery sheath for thedelivery of the stent to pass through the lesion, are pre-dilated routinely When pre-dilation is performed, the

stenosis is pre-dilated only enough to allow the particular

delivery sheath to pass through the stenotic area Whenthe vessel adjacent to the stenosis (either proximal or dis-tal to the obstruction) is significantly larger than the pro-posed initial delivery balloon for the stent, pre-dilation

unequivocally should not be performed A “successful”

pre-dilation of a stenotic area temporarily will dilate the

area acutely, but it also temporarily makes the area of

the stenosis very compliant and even “patulous” When a

stent is implanted in this patulous or “softened” area, the

stent does not fix securely to the now elastic walls, even

when it is fully expanded and is in the proper position As

a consequence, the stent/balloon can be displaced very

easily either during the balloon inflation or, even more

likely, during the attempted removal of the balloon from

within the lumen of the stent after the implant Any

move-ment of the stent immediately after implant usually

results in migration of the stent to a non-stenosed area of

the vessel or, even worse, results in a stent “free floating”

in a vessel/chamber

The main argument in favor of pre-dilation of a lesion in

which a stent is going to be implanted, is to ensure that the

balloon/stent combination can open the lesion sufficiently

during the implant/expansion of the stent to allow

removal of the balloon from the stent after implant The

inability to dilate the lesion during the implant of the

balloon/stent combination can leave not only the original

vessel stenosis, but also a stent with the same stenosis in it

The presence of the stent on the balloon does not add any

additional dilating force or dilating capability in addition

to that of the balloon alone The expanded intravascular

stent only maintains the degree of dilation that is achieved

acutely by the particular balloon When a significant

re-sidual stenosis persists in the stent/vessel after a stent is

implanted with a usual “standard-pressure” balloon, the

original implanting balloon is replaced with a

high-pressure balloon and the dilation of the stent/vessel

re-peated Very few (no!) residual stenoses do not respond

to a balloon dilation when a non-compliant, high-pressure

balloon is used for the reinflation and the balloon is

inflated to 20 to 25 atmospheres within a stent! This is true

particularly when the attempt at re-dilation is six, or more,

months after the original stent implant

Pre-dilation of the area and the diameter of the

pre-dilation constitute a judgment decision during each stent

implant procedure The decision is individualized in the

catheterization laboratory as the anatomy is visualized and

sized When pre-dilation of the vessel is performed before

a stent implant, there is one major “rule” for the pre-dilation.

The pre-dilation of any stenotic lesion which precedes the

implant of an intravascular stent should be only to a

dia-meter that will accommodate the delivery sheath and which

is significantly smaller in diameter (at least 3 mm smaller in

diameter) than the diameter of the adjacent vessel or to the

diameter to which the stent is to be expanded at its initial

implant In order to ensure fixation of the stent into some

residual, more rigid tissues in the vessel wall, pre-dilation

with a minimal diameter balloon ensures that the balloon

that is used for the delivery of the stent can be larger and

can expand the stent to a diameter which is definitely

larger than the pre-dilated (“softened”) stenotic area.

The pre-dilation is performed over the same

Super-Stiff™ wire over which the long sheath/dilator eventually

will be delivered Once the wire is securely in place, a

stand-ard pressure dilation balloon is advanced over the wire to

the obstruction The pre-dilation balloon used is only 2–

3 mm larger in diameter than the diameter of the stenosis in the vessel and is at least 3 mm smaller than the adjacent ves- sel, which should be the anticipated implant diameter of the

stent The pre-dilation documents at least some “give” tothe stenosis in the vessel as well as opening the vessel toaccommodate the large sheath for the stent delivery After

a pre-dilation is performed, the Super Stiff™ wire is tained in its secure distal location, while the separate balloon used for the pre-dilation is withdrawn, leavingthe wire in place across, and well beyond, the stenosis

main-If a very tight area of stenosis cannot be pre-dilated at all with a standard-pressure balloon, a high-pressure balloon which is similar in size to the standard-pressure balloon is

used over the same wire in a repeat attempt to pre-dilate

the stenosis to the minimal diameter that will accommodate

the delivery sheath Pre-dilation with the high-pressure,but smaller, balloon ensures that if the standard, lower-pressure balloon for the delivery of the stent does not fullyexpand the area of stenosis, the area of stenosis will beexpanded to at least the diameter of the high-pressure,pre-dilation balloon This newly permitted increase in thediameter provides sufficient evidence to be certain that

the implanting balloon can be removed from a partially

expanded (but secured) stent without displacing the stent

Long indwelling sheath stent delivery technique

A long sheath/dilator set which will accommodate theparticular balloon/stent combination is advanced overthe pre-positioned Super Stiff™ wire and past the area of

stenosis which usually has not been pre-dilated The tip

of the sheath is positioned at least several centimeters distal

to the area of obstruction in the vessel The delivery of the sheath to the lesion and securing the sheath in posi-tion without creating kinks in the sheath, particularly

to branch pulmonary artery lesions, often is the mostdifficult and challenging part of the entire procedure forthe implant of an intravascular stent Once the sheath and

dilator are in position with the tip of the sheath well

beyond the lesion, the Super Stiff™ wire in the distal sel and the long sheath are fixed in place while the dilator

ves-is slowly and carefully withdrawn over the wire and out

of the sheath The sheath is allowed to bleed back from the

side port on the back-bleed valve until it is clear of all air

and possible clotsaremembering that the large, long

sheaths hold 10–15 ml of fluid (or air and/or clot!) Once

cleared by “passive drainage”, the sheath is flushed

thor-oughly by hand and then is attached to a continuous slow

flush to prevent the development of clots in the largepotential dead space within the sheath and around thewire After any pre-dilation is accomplished and as soon

as the delivery sheath is in position, if not administered

earlier, the patient is administered systemic heparin in a

dose of 100 mg/kilogram of body weight

If a long sheath with an attached back-bleed valve/

flush port or a separate back-bleed valve/flush port

that which will accommodate the delivery catheter and

fit on the long sheath is not available in the particular

catheterization laboratory, the massive bleeding which

would occur from the open sheath can be prevented with

a “make-shift” solution The bleeding through a

non-valved sheath with a wire within it is stopped effectively

(and temporarily) with a “rubber-shod” Kelly™ clamp

placed across the sheath (containing the wire) just outside

of the body where the sheath exits the skin This prevents

the massive blood loss around the wire and through the

sheath after the dilator is removed from the sheath Of

equal importance, it prevents air from being sucked into

the sheath during a deep inspiratory effort by the patient

The clamp on the sheath does not allow any acute or

continuous flush of the sheath, and the clamp indents the

sheath, but only in an area outside of the body where the

clamp is applied This indentation in the sheath does not

interfere with the passage through that segment of the

sheath that is outside of the body and can be straightened

manually, nor with the eventual delivery of the stent

Of most importance, the “external” indentation does not

involve any areas that are in tight curves or bends in the

sheath in the course of the sheath to the target site

When a separate, detachable back-bleed valve, which is

not built onto the sheath, is used for a stent delivery on a

large sheath with no built-in back-bleed valve, the balloon

alone is passed through the detached, separate back-bleed

valve and is slid back onto the shaft of the balloon dilation

catheter before the stent is mounted on the balloon In this

way the stent mounted on the balloon does not have to be

forced through the smaller diameter lumen of the

remov-able, back-bleed valve After the stent has been mounted

on the balloon, the stent/balloon unit is introduced

com-pletely into the non-valved sheath, the pre-mounted

back-bleed valve is advanced forward on the shaft of the

catheter onto the proximal hub of the sheath, and attached

to the hub The clamp on the sheath is released, the sheath

is allowed to bleed back thoroughly through the side port

of the attached back-bleed valve, and then the side port is

attached to the flush system

The exact stent and balloon that are used depend upon

the current, desired and eventual adult size of the vessel

and the location of the lesion in the vessel For all vessels,

a stent always is used which eventually can be dilated to

the eventual adult diameter of the particular area of the

vessel The length of the stent depends upon the length of

the actual lesion, the expected shrinkage in the length of

the stent with full expansion, the curvature of the vessel,

and the distances within the vessel before any branching

or bifurcations The exact anatomy is defined ically or, when there is any question, by inflating the

angiograph-“sizing” angioplasty balloon in the precise area at a verylow pressure

In choosing the appropriate stent for a particular lesion,the operator must always consider the amount of shrink-age in the length of the stents with each increase in dia-meter of the stents This is particularly important with the J & J™ Palmaz™ (Cordis Corp., Miami Lakes, FL) andGenesis XD™ stents (Johnson & Johnson–Cordis Corp.,Miami Lakes, FL), which shrink as much as 50% wheninflated to their largest diameters Shrinkage in length tosome degree must be considered with almost all stents.When a stent is to be expanded to 15 mm or larger in dia-meter, in order to account for the shrinkage, the stent usedoften must be longer in its collapsed state than the length

of the vessel where it is to be implanted This shrinkage inlength makes it extremely important that the balloon andstent are positioned precisely over the exact lesion at thebeginning of, and maintained in that position throughout,the expansion of the stent during its implant With a stentproperly and precisely placed on the delivery balloon,

the shrinkage usually, but not necessarily, is symmetrical

from both ends of the stent As a consequence, most loon/stent inflations should be slow and observed verycarefully so that any asymmetric expansion or movement

bal-in the position of the stent relative to the anatomy can beadjusted before the stent is fully expanded and fixedsecurely in an abnormal position The expected shrinkage

of a stent occasionally is used to the operator’s advantage,utilizing the further decrease in length with furtherexpansion of a stent to move the ends of the stent awayfrom crossing or branching vessels The use of a BIB™ bal-loon (NuMED Inc., Hopkinton, NY) is helpful in order toallow some purposeful adjustment for an asymmetricalinflation or shrinkage after the stent has been expanded toonly half of its final diameter

The balloon is chosen specifically for the stent that isbeing used and the diameters adjacent to the area of

implant while the exact stent is chosen for the particular

anatomy of the lesion as well as the diameters of theimmediately adjacent vessels To prepare the balloon forthe stent, the balloon lumen is attached to the inflationdevice and the balloon is inflated partially, but not to ahigh pressure The balloon is cleared of air by repeatedpartial inflations/deflations while holding the balloon in

a vertical position with the tip of the balloon facing down.

Once the balloon is cleared of air, the balloon is deflatedslowly while simultaneously refolding the balloon manu-ally around the shaft of the catheter Once the balloon

is refolded as smoothly as possible, the balloon is tained on “negative pressure” by withdrawing theplunger of the inflation device and locking it in the fully withdrawn position The appearance of a continual

main-stream of tiny bubbles after applying negative pressure to

the balloon with an inflation device indicates a leak in the

balloon or the inflation system The source of any leak is

identified and eliminated before proceeding, even if it

requires replacing the balloon or the inflation device

There are some special preparations for the BIB™

bal-loons Each BIB™ balloon catheter has three lumens: one

lumen (with a blue hub) to the inner balloon, one lumen

(with a white hub) to the outer balloon, and a central

catheter lumen of the catheter itself (with a green hub)

In the original BIB™ balloons, where the central lumen

passed through the area of the balloons and before it

passed out through the tip of the catheter, the tubing of the

central lumen was very narrow and thin walled This

nar-row tubing allowed the collapsed balloons to compress to

a diameter only slightly larger than the diameter of the

catheter shaft, but did not provide much longitudinal

sup-port in that area when there was no wire in this lumen To

compensate for this during the preparation of the

bal-loons, each balloon catheter comes with a blunt, solid

metal, 0.035″ stylus This metal stylus is inserted into the

distal end of the catheter lumen during balloon

prepara-tion and while the stent is being crimped on the balloon

The stylus passes through the area of the balloon(s) and

back into the shaft of the catheter well proximal to the

bal-loons and, in this position, keeps that area of the catheter

and the balloons very straight and elongated

For preparation of BIB™ balloons, both balloon lumens

are connected to manometered inflation devices The

inner balloon is inflated and cleared of air and then

the outer balloon is inflated and cleared separately Once

the balloons have been prepared, cleared of all air and

rewrapped around the catheter, the balloon lumens are

opened to neutral pressure and the stylus is removed The

stent is passed over the refolded balloons, the stylus is

reinserted, and both balloons are again placed on negative

pressure Since the stent over the balloons covers the

radio-opaque “markers” on the catheter within the

bal-loons, the BIB balloons with the stent mounted are viewed

under fluoroscopy in order to align the stent precisely and

evenly within the marks within the balloons The stent

then is compressed (crimped) over the balloons by hand

exactly as with any other stent–balloon combination The

stylus remains in the catheter during the “crimping” and

until just before introduction over the delivery wire

Any balloons that have a Silicon™ or other “slippery”

coating also require “pre-preparation” before a stent is

mounted on them The balloon is inflated until it is tense

and then the “slippery” coating is rubbed off the balloon

surface very vigorously with a dampened, 4 × 4 gauze

sponge Once it is “rubbed clean” the balloon is manually

rewrapped over the catheter as it is deflated When the

balloon has been cleared of air, the balloon is placed

on negative pressure and simultaneously is rotated and

“refolded” onto the shaft of the catheter in order to lapse the balloon maximally onto the catheter shaft Someslight “irregularities” on the surface of refolded balloonsactually are desirable when using balloons for the deliv-ery of stents The irregular surface of the balloon helps tokeep the stent, which is hand-crimped on the balloon,from sliding on the balloon during its passage through thesheath Before the stent is advanced over any balloon for mounting on the balloon, the stent and surface of theballoon are both coated with undiluted contrast solution

col-As the contrast dries, it becomes very sticky and serves as

a “glue” that will help to hold the stent on the balloon

To prepare the stent for mounting on the delivery loon, the entire length of the stent is dilated sufficiently toallow the stent to pass easily over the balloon, and one end

bal-of the stent is flared even wider by inserting the tip bal-of alarge dilator (the dilator from the delivery sheath) into oneend of, and advancing it through the length of, the stent

As the dilator is withdrawn from the end of the stent, thedilator is angled slightly and rotated around within theproximal tip of the stent, which, in turn, “flares” or makes

a “funnel-like” opening in one end of the stent Whenmuch larger delivery balloons are used, the entire stent

is dilated even further before introducing the stent by gently advancing an even larger dilator into, and through, the stent The dilation and flaring of the stent facilitateadvancing the stent over the balloon and help to preventthe ends of the stent from catching on the folds of the bal-loon With the Palmaz™ J & J™ stents, this is essential toprevent the puncture of the balloon by a sharp tip at theend of the stent

With negative pressure applied to the balloon lumen,the tip of the balloon catheter is introduced carefully into

the flared end of the stent and while the stent is allowed to

rotate slowly and very slightly (less than 360°) to pond to the direction of the folds of the balloon, the bal-loon is advanced very gently into the stent The catheter

corres-and balloon always should slide freely into the stent The

introduction of the stent over the balloon is performedvery gently and slowly to prevent a sharp tip at the end of

a stent from digging into, and puncturing, the balloonduring the mounting process Particular care is necessarywith the J & J™ Palmaz™ stents (Johnson & Johnson,Warren, NJ) which all have multiple sharp tips at each end

If the stent catches on the balloon at all, the stent is drawn, the balloon is re-formed or the stent dilated/flaredfurther The stent is advanced over the balloon until it is

with-positioned over the exact center of the length of the balloon.

The stent is centered lengthwise as precisely as possible byaligning the ends of the stent with, or equally between, themetal markers on the shaft of the catheter beneath the bal-loon material When there is any question about the exactpositioning of the stent on the balloon, the stent/balloonshould be visualized under fluoroscopy

Once the stent is centered exactly on the balloon, the

metal stylet of the BIB™ balloons is introduced into the

distal end of the catheter lumen of the balloon catheter

and pushed far enough into the distal end of the catheter

lumen of the balloon catheter to be entirely proximal to

the balloon This stylet within the lumen supports the

lumen of the catheter during the subsequent forceful

com-pression of the stent over the balloon Strong negative

pressure is maintained on the balloon lumen while the

connecting tubing and the inflator are inspected carefully

for any balloon leaks A new puncture or leak is indicated

by a continual stream of small bubbles flowing into the

tubing or the inflator as the negative pressure is applied

Once assured that there are no leaks, the stent is

com-pressed (crimped) uniformly on the balloon by manual

finger compression There are no “crimping tools”

avail-able that are applicavail-able universally for the large variety of

stents, balloon sizes, and balloon types or for the different

diameters of the catheter shafts of the different large

balloon dilation catheters used for the large variety of

congenital lesions As a consequence, the crimping of all

non-pre-mounted stents is performed by hand Several

more drops of contrast are placed on the surface of the

stent before the manual crimping on the balloon is started

Starting with light finger pressure, finger pressure is

gradually increased while moving the fingers over the

entire length and around the circumference of the stent

The circumference of the stent is squeezed onto the

bal-loon as the stent/balbal-loon is rolled between the fingers

Once the stent is relatively smooth and secure on the

bal-loon, then the fingers are squeezed as tightly as possible

and repeatedly over the entire surface of the stent/balloon

as the combination is rotated between the fingers The

process is repeated using the tips of the fingernails to

compress the individual longitudinal struts forcefully

between the circumferential “bands” of the stent This

fingernail compression creates a slightly irregular surface

on the mounted stent, which, in turn, helps to secure the

stent on the balloon, but does not affect the eventual stent

expansion or strength

The short length of plastic tubing which is present over

the balloon in its sterile package is occasionally used as a

“smoothing” tool over the stent once it is mounted on the

balloon When the stent has been compressed over the

bal-loon, the plastic tube is advanced over the combination

of the balloon/stent The tube over the stent/balloon is

compressed manually between the fingers as tightly as

possible while the tube, stent, and balloon are rotated

between the fingers However, this step usually is not

nec-essary and does not crimp the stent as tightly as direct

finger compression on the stent

Once the stent is compressed securely on the balloon,

several more drops of undiluted contrast solution or

albu-min solution are spread on the surface of the balloon–stent

combination The additional contrast is allowed to drybriefly on the surface of the balloon–stent This serves asadditional “glue” to help retain the stent on the balloonand keep it from “sliding” on the balloon during deliverythrough the sheath The contrast “glue” works most effect-ively if it is allowed to dry for 15–20 minutes

Stent delivery over a wire and through a pre-positioned sheath

The delivery of the stent/balloon combination to thelesion, over a pre-positioned stiff wire and through a pre-positioned long sheath, is the original and establishedtechnique for the delivery of stents to the various congeni-tal lesions This technique is the most tested and reliabletechnique available for the delivery of the current stents.With the sheath and wire fixed in their position beyondthe area of obstruction, the balloon catheter with themounted stent is introduced over the proximal end of thewire and advanced to the valve of the sheath The intro-duction of the balloon with the mounted stent into andthrough the valved sheath depends on the length and type

of stent The J & J™ Palmaz™ stents, which are longerthan 3 cm, can be pushed directly through the back-bleed

valve by gripping the most proximal end of the stent very

tightly with the tips of the fingers As the proximal tip ofthe stent is squeezed tightly and continuously in order

to maintain the stent in its exact position on the balloon,

the entire length of the stent is advanced through thevalve of the sheath, and the combination stent/balloon isadvanced into, and all of the way through, the attachedback-bleed valve chamber and into the sheath There is asmall “flare” at the proximal end of the sheath within thedistal end of the back-bleed valve housing (chamber)where the back-bleed apparatus is attached to the sheath(Figure 22.7) This flare of the sheath creates a flange or

“ridge” within the back-bleed valve chamber between thedistal end of the valve housing and the proximal end ofthe sheath within the valve “chamber” This ridge is notvisible from outside of the back-bleed housing, but cancatch the distal end of the stent and block the passage ofthe mounted stent from passing into the lumen of thesheath from the back-bleed valve chamber Longer stents

can be held securely at the proximal end of the stent with

the tips of the fingers and supported on the balloon as

the stent is advanced all of the way through the “valve” and

past this ridge.

The shorter P 108, 188, and 204 stents are too short tomaintain a grip with the fingers on the proximal end of the

stent as it is advanced all of the way through the bleed valve and past the flange When introducing the

back-shorter stents is attempted by just holding the stent withthe fingers, the stent is easily displaced proximally off

of the balloon as the proximal end of the stent passes

through the valve beyond the grasp of the fingers This is

overcome by using the short “metal introducing tube”

supplied by J & J™ (Johnson & Johnson, Warren, NJ), or

a short, cut-off length of sheath as an introducing sleeve

(see Figure 22.1) The short length of “introducer” sheath

should be the same diameter as the delivery sheath, made

from a fairly stiff sheath material and approximately five

centimeters long The proximal, cut, end of the short

seg-ment of sheath can be dilated with a forceps to flare the

end slightly The balloon with the mounted stent is

intro-duced very carefully into the flared end of this sleeve until

the stent is completely within the sleeve The sleeve along

with the contained balloon/stent are all held together and

are passed through the back-bleed valve and into the long

sheath until the sleeve seats on the flange between the

valve apparatus and the proximal end of the sheath (see

Figure 22.1) The balloon, stent, and catheter are advanced

out of the sleeve and into the shaft of the long sheath The

sleeve is withdrawn out of the valve and back to the hub

on the shaft of the balloon catheter The introduction of the

stent/balloon through the short sleeve can be used for the

P 308 stents, and may make their introduction through

the valve more secure The short sleeve should definitely

be used with all of the open-cell stents (ev3, Plymouth, MN)

The pattern and the “looseness” of the cells of the

open-cell stents cause them to catch on the back-bleed valve

itself and cause the cells to pull apart if they are pushed

directly through a back-bleed valve

When a long sheath with a separate and non-attached

back-bleed valve/flush port is the only long sheath available,

the balloon and the balloon catheter are passed through the

removable back-bleed valve/flush port separately before

the stent is mounted as described previously The balloonwith the mounted stent is introduced into the open end ofthe stent and the back-bleed valve, which is on the moreproximal shaft of the catheter, is pushed forward on theshaft of the catheter and attached to the large sheath with

a continuous flush delivered to the pre-mounted bleed valve The remainder of the stent delivery thenbecomes identical to the delivery through a long sheathwith a built-in attached back-bleed valve

back-Once the proximal end of the stent/balloon combination

has been introduced and advanced several centimetersbeyond the valve and hub of the sheath, the balloon isinflated very gently (~1 atmosphere) with the inflator andthe inflator is locked to maintain this pressure in the bal-loon This minimal pressure to the balloon expands theexposed shoulders of the balloon, which extend beyondeach end of the stent, very slightly, without expanding thestent at all This is particularly useful when the balloon

is the same length or slightly longer than the stent Theslightly expanded balloon and the “exposed” shoulders ofthe balloon help to keep the stent from sliding proximally

on the balloon as it is advanced through the sheath Unlessthe balloon is inflated too vigorously, this still allows the balloon to pass easily through the sheath If the bal-loon/stent does not move easily within the straight area ofthe sheath, the balloon has been inflated with too muchpressure, and some of the pressure on the inflator should

be released This slight inflation of the ends of the balloon

is important, particularly where there is a very tortuouscourse of the delivery sheath through tight bends in thevascular system

While frequently observing the balloon/stent tion within the sheath as well as the position of the tip ofthe wire and sheath and the course of the wire and sheath

combina-on fluoroscopy, the ballocombina-on catheter with the mountedstent is advanced over the wire within the sheath to theinvolved narrowing in the vessel As long as the wire andsheath are maintained securely in place, advancing theballoon and stent is usually accomplished quite easily It is

important to repeatedly observe the entire course of the

sheath as well as the tip of the sheath and wire while the

catheter and the balloon/stent are being advanced withinthe sheath Occasionally, the “circumference” of a long

curve in the course of the sheath/wire as it passes through the heart is widened as the balloon, stent, and catheter are

pushed against the outer circumference of any curve inthe sheath while it is passing through a dilated chamber orvessel within the heart As the balloon, stent, and catheter

push on and increase the curvature of the sheath, the

dis-tance along the wire from the skin entry site to the lesion

lengthens If the increasing circumference of this curve inthe sheath/wire and, in turn, the actual length of the dis-

tance to the lesion are not noticed and not compensated for

by advancing the sheath and wire along with the catheter at

Figure 22.7 Flange (or flare) on proximal end of sheath within the

back-bleed valve chamber.

the skin, the tip of the sheath and the wire will be

with-drawn out of their secure positions distal to the lesion As

soon as this “widening of the circumference” of the curve

begins to occur, instead of the sheath and wire remaining

firmly fixed outside of the body, the sheath and wire

outside of the body are advanced along with the

bal-loon/stent/catheter just enough to compensate for the

increased length being caused by the large curvature

within the heart

Once the stent and balloon have been advanced

through the sheath to the area of the lesion, the stent

(on the balloon) is centered exactly at the area of maximal

narrowing The slight pressure in the balloon lumen

is released and the balloon deflated completely before the

sheath is withdrawn off the stent/balloon With the

stent/balloon still within the sheath and with the guide

wire still buried far out into the lung parenchyma, the

wire, catheter, and balloon/stent are fixed in this location

while the sheath alone is carefully withdrawn off the

balloon/stent/catheter/wire combination This uncovers

the stent on the balloon over the wire centered in the

proper location in the area of narrowing

After withdrawing the sheath, it is important to repeat a

selective angiogram through the separate venous catheter

either within, or just proximal to, the lesion in order to

verify the exact positioning of the stent in the stenosis

Because of the stiffness of the wire, the catheter and the

sheath, often there is distortion of the vessel and a change

in the curvature and position of the wire/balloon/stent

combination relative to the stenosis or to relatively fixed

landmarks in the thorax after the sheath has been

with-drawn This can displace the stent/balloon away from the

exact central area of stenosis compared to the location

before the wire was introduced The repeat selective

angiocardiogram identifies any changes in relative

posi-tions and allows the stent/balloon to be readjusted into

the precise area of narrowing Repositioning of the

stent/balloon/catheter in the area is similar to the

reposi-tioning of a balloon/catheter for angioplasty The stent,

balloon, and catheter are advanced over the fixed wire to

advance the stent further into the lesion, but in order to

withdraw the stent/balloon/catheter, the wire alone is pushed

forward forcefully As the wire advances, it pushes the

stent/balloon/catheter backwards while, at the same

time, keeping the wire forced forward into the distal

loca-tion in a very secure posiloca-tion

During the passage of the balloon/stent/catheter

through the sheath, occasionally the stent slips on the

bal-loon and is displaced proximally on the balbal-loon If this

displacement is less than 1–2 mm and the stent is still

completely over the balloon, it usually is of little or no

con-sequence However, the balloon and stent positions should

be inspected very carefully while the balloon and stent are

still within the sheath and before the sheath is withdrawn If the

stent is displaced more proximally on the balloon, the stent

still may be in its proper position within the lesion, but the

distal end of the balloon, off of which the stent is displaced,

will be positioned further into the distal vessel and awayfrom the narrowing A distal positioning of the balloonusually results in the balloon/stent combination milkingbackwards before the stent even begins to expand duringthe initial balloon inflation This results in the stent’s beingdisplaced and implanted in an improper location If the

“extra distal balloon” extends into a small distal vesseland the distally displaced balloon does not milk back out

of the vessel, the expansion of the balloon can result inrupture of the small vessel

If the stent is displaced more than 1–2 mm on the balloon, and certainly if the stent extends completely offthe balloon at all while the stent and balloon are stillwithin the sheath, the implant procedure is abandoned

temporarily and the sheath is not withdrawn off the

balloon/stent combination With the balloon/stent stillwithin the sheath and with the stent now positioned overonly the proximal end of the balloon, the balloon again isinflated very slightly This inflates only the distal end

of the balloon and creates a larger “shoulder” of balloon

distal to the stent The entire catheter/balloon/stent is

withdrawn through the sheath, over the wire, and out ofthe body The larger “shoulder” of the balloon, which isnow completely distal to the displaced stent, helps to keepthe stent from sliding distally off the balloon as the combi-nation is withdrawn through, and out of, the sheath Evenwith the “distal shoulder” on the balloon the stent oftencatches at the valve of the sheath and is retained in thevalve chamber of the sheath after the balloon has beenwithdrawn Usually, the very end of the stent is visiblejust within the valve and still over the wire When the end

of the stent is visible just within the valve, a tip of the ible end of the stent is grasped with a small forceps andpulled out through the valve

vis-If the stent cannot be retrieved from within thesheath/valve, the entire sheath must be withdrawn overthe wire Once the sheath is completely out of the bodyand off the wire, the stent is pushed forward, through andout of the distal end of the sheath with a dilator or ballooncatheter Once the stent is retrieved from the withdrawnsheath, the dilator is replaced in the sheath and thesheath/dilator is re-advanced over the wire into the vessel

and to the lesion If the sheath is damaged at all, a new

sheath/dilator set is used

Unless it was damaged in the removal process, theretrieved stent is re-mounted on the same or a new bal-loon When re-mounted, the stent is positioned 1–2 mm

forward (distally) of the center of the balloon This leaves

the stent mounted slightly more distally on the balloon

with more “shoulder” exposed “behind” and more imal to the stent toward the shaft of the catheter The

prox-balloon catheter with the re-mounted stent is

reintro-duced over the wire, into and through the back-bleed

valve of the sheath, and advanced several centimeters into

the sheath The balloon is again inflated minimally (with

approximately one atmosphere of pressure) The

“for-ward” positioning of the stent on the balloon allows more

of the proximal “shoulder” of the balloon to expand slightly

behind the stent, which, in turn, helps to prevent the stent

from sliding backward as the balloon/stent is advanced

through the sheath Once the balloon/stent has been

advanced to the proper position as verified

fluoroscopic-ally, the balloon again is deflated before the sheath is

withdrawn off the balloon/stent

Very rarely, as the sheath is being withdrawn off of

the stent/balloon, the stent again slides backward

(prox-imally) on the balloon along with the sheath or,

inadvert-ently, the stent/balloon is exposed with the stent already

displaced proximally on the balloon In this circumstance,

after the sheath is completely off the stent but still partially

over the proximal balloon, the sheath is gently

read-vanced over the balloon Usually, the edge of the distal

end of the sheath catches on the proximal end of the stent

and does not allow the stent to be withdrawn back into the

sheath By continuing to advance the sheath forward very

gently, the stent can be pushed forward, and often can be

positioned back onto the proper location on the balloon!

This maneuver must be performed very gently and

care-fully with no excessive force If the stent does not move

forward easily, it suggests that the sharp distal ends of the

stent struts are caught on the balloon Any excessive force

applied to the sheath can push one of the sharp tips of the

end of the stent into the wall of the balloon and puncture

the balloon This is a particular problem with the J & J™

Palmaz™ stents with the very sharp tips at both ends

Fortunately, even the Palmaz™ stents and all of the other

stents can usually be re-advanced over the balloon quite

safely by using this maneuver with the tip of the sheath

The sheath is withdrawn off the proximal end of the

balloon but no further The sheath positioned in close

proximity to the balloon helps to support the shaft of the

balloon catheter during the implant Once the stent is in

the exact, proper position in the stenosis and its correct

position on the balloon has been verified, the balloon is

inflated slowly to its maximum advertised pressure and

hopefully to the maximum diameter of the balloon

During the inflation the stent is observed continuously

and recorded on biplane angiography or biplane stored

fluoroscopy The inflation of the balloon expands the stent

into the stenosed area of the vessel to the diameter of the

implanting balloon If there is even the suggestion of stent

displacement during the initial slow inflation, the

in-flation is stopped and the stent/balloon repositioned

correctly within the stenosis using manipulations of the

catheter, wire or sheath Once the stent is expanded fully

or the balloon has reached its maximum pressure, the balloon is deflated rapidly Often, there is some waist orincomplete expansion of the stent with the first inflation ofthe balloon; however, with accurate prior sizing and posi-tioning, the stent will be centered on the lesion and fixedsecurely in the vessel The deflated balloon is repositionedover the wire very slightly forward or backward and theinflation is repeated several times to achieve maximalexpansion of the entire length of the stent with the particu-lar balloon

After implanting the stent securely in the area of stenosis and while the balloon is still within the stent, thestent position and fixation are confirmed with a repeatangiogram through the adjacent catheter With the balloon still positioned within the stent, the balloon isreinflated at a low pressure Then, simultaneously, as theballoon is being deflated slowly and with the balloon stillwithin the stent, the long delivery sheath is re-advancedgently and gradually over the balloon and into the stent asthe balloon deflates within the stent10 The inflated bal-

loon within the stent centers the proximal shaft of the loon catheter and the advancing edges of the tip of the sheath

bal-within the lumen of the stent This “centering” keeps theedge of the distal end of the sheath from catching on theproximal end of the stent as the sheath is reintroducedinto and through the stent Often, as the sheath tip ispushed against the balloon and as the balloon is deflating,the balloon and the following tip of the sheath slide for-ward together and through the stent before the balloondeflates completely This still accomplishes the goal of thesheath advancing completely through the stent withoutcatching on, or dislodging, the stent

Once the sheath is in or completely through the stent,the balloon is deflated completely by applying negativepressure to the balloon lumen When the balloon has been

deflated completely, the negative pressure is released from

the inflating syringe The balloon is withdrawn over thewire and into the sheath with the balloon lumen on “neu-tral” pressure while the balloon catheter is rotated veryslightly in the direction of the balloon folds (determinedearlier while preparing the balloon), and it is withdrawninto the sheath The release of the strong negative pressure

“softens” the folds or “wings” on the deflated balloon.When the sheath can be repositioned and maintained in

its position through the stent, the sheath allows the balloon

to be withdrawn through the stent while the stent wallsare “protected” completely by the sheath from any roughfolds or “wings” on the deflated balloon as the balloon iswithdrawn With the long sheath through the stent, acatheter or a new, larger or different balloon can easily beadvanced reliably and safely through, or into, the newlyimplanted stent without danger of dislodging the stent.This balloon-assisted procedure for re-entering the stent

is extremely valuable in even the most straightforward

stent implant procedures but it is particularly important

when there are any curves in the vessel immediately

prox-imal to the area of the stent10 The greater the angle or

cur-vature of the vessel entering the stent, the more essential

the balloon-assisted re-entry technique becomes The stiff

guide wire through the stent tends to “remain straight”

and to orient itself tangentially across a curved vessel (and

stent) This consistently forces the wire, catheter, and

sheath against one edge of the proximal end of the stent,

which, in turn, prevents even a finely tapered dilator

or catheter from entering the stent after its implant The

balloon-assisted procedure for re-entering the stent with

the sheath is now the standard technique used after

essen-tially every stent implant

Once the deflated balloon has been withdrawn from the

stent, preferably through the sheath with the wire and

sheath remaining through the stent, the balloon catheter is

withdrawn from the vessel and out of the body through

the sheath The necessity for further dilation or for placing

additional stents is determined from pressure

measure-ments and repeat angiography while the sheath is still

passing through the stent With the sheath in place within

the stent, any subsequent steps in the procedure are far

more straightforward If a partially inflated stent is fixed

in the vessel and the vessel and stent are still stenotic, the

initial implanting balloon is replaced with a high-pressure

balloon to further expand the stent and vessel together

Occasionally the sheath cannot be re-advanced into the

stent even over the actively “deflating” balloon, and on

withdrawal of the balloon through the stent, the balloon

catches on, and begins to dislodge, the stent In this

situ-ation the sheath is re-advanced until the edge of the distal

end of the sheath purposefully is pushed against the proximal

end of the stent and purposefully caught against the stent.

The sheath that could not be advanced into the stent is

now caught on the end of the stent and is used to

“but-tress” the stent in its position in the vessel With the sheath

fixed in this position against the stent, the stent is held in

place as the balloon is carefully withdrawn Simultaneous

rotation of the balloon catheter facilitates the withdrawal of

the balloon out of the stent and into the sheath It can be

helpful to advance the balloon beyond the stent, reinflate

the balloon at least partially, and then deflate the balloon

while rotating the balloon catheter to help “refold” the

balloon Once refolded, the strong negative pressure is

released from the balloon before attempting to withdraw

the balloon from the stent

If the sheath cannot be re-advanced into the stent while

the balloon is deflating within the stent, but the balloon

can be withdrawn out of the stent, the balloon is

with-drawn out of the stent, through the sheath and out of the

body The long dilator is reintroduced into the sheath and

an attempt can be made at reintroducing the combined

sheath/dilator into and through the stent Unfortunately,

even with an apparent tight and smooth fit of the tip of the dilator over the wire and the tip of the sheath over thedilator, the tip of the dilator or sheath often catches on theproximal end of the stent and cannot be reintroduced intothe stent without dislodging the freshly implanted stent.Occasionally the use of a new dilator, which is one size

larger than the sheath (particularly the 11- and 12-French

sheaths) and with a different curve formed on the tip of thedilator, will facilitate the sheath and dilator re-enteringthe stent Advancing or slightly withdrawing the wireseparately while simultaneously advancing the sheath/dilator, occasionally changes the angle of the wire as itenters the stent enough to allow the tip of the dilator and subsequently the sheath to enter the stent However,

remarkably, the very tiny interspace between the wire and

dilator or sheath and dilator frequently is very effective at

catching on the sharp, exposed end of the stent and totallyprevents reintroduction of the sheath into the stent Thisproblem provides the rationale behind the reintroduction

of the sheath into the stent over the initial balloon as it is

being deflated within the stent whenever it is possible.When the balloon cannot be withdrawn into the sheathonce it has been withdrawn out of the stent, both the bal-loon and sheath are withdrawn from the body over the

wire with the wire still fixed securely through the stent into the

vessel far distal to the lesion Even when the balloon cannot

be completely withdrawn into the sheath, at least the tially refolded, proximal “shoulder” of the balloon usu-ally can be withdrawn into the distal end of the sheath,which, in turn, “covers” the rough folds in the shoulder atthe proximal end of the balloon and partially protects thevein and tissues as the combination sheath and balloonare withdrawn This partial covering of the shoulder ofthe balloon allows the partially folded balloon to be with-drawn through the vein puncture site, subcutaneous tissues, and skin without causing significant vessel/tissue

par-damage Again, it is important to release any negative

pres-sure from the collapsed balloon in order to “soften” the

exposed folded edges or “wings” on the balloon

Once the balloon and large sheath are out of the body

and off the exchange wire, either a new long sheath or a

new short sheath/dilator of the same diameter as the

pre-vious long sheath is introduced over the wire, into the

vein The new, large sheath prevents bleeding and is less

traumatic to the vein for any subsequent catheter or loon introductions In the past, large balloons for subse-quent or further dilations were introduced into the veindirectly over the stiff exchange wire without a sheath.However, this is no longer recommended The roughwalls of a large “folded balloon” passing directly into the tissues and particularly on withdrawal from the ves-sel/tissues are significantly more traumatic to the vesselthan a larger diameter, but fixed, indwelling and im-mobile sheath

bal-The larger balloons used for re-dilation of a stent,

particularly the 15 and 18 mm balloons, are prepped

“negatively” or at most, minimally inflated during their

preparation before their introduction in order to prevent

the development of the large “wings” or rough irregular

shoulders from a previously fully inflated/deflated

balloon When introduced through a short sheath and

advanced over the wire without a long sheath passing

through the stent, the balloon must be advanced very

carefully into and through the stent Even though the

proximal end of the stent is wide open, because of the

tend-ency of the Super Stiff™ exchange wire to “straighten”,

the wire usually presses against one edge at the end of the

stent and the tip of the balloon, or the folds of the balloon

almost always catch on the ends of the proximal wires of

the stent Again, slight, alternating traction with pushing

or advancing the wire as the balloon is advanced, often

changes the angle and relative positions of the

wire/bal-loon/catheter as the tip of the balloon enters the stent In

particular, as traction is applied to the wire, the wire often

is pulled away from the wall of the stent This allows the

tip of the balloon to enter the stent first and then the entire

balloon to pass into and through the stent This traction on

the wire must be performed very cautiously since any

traction on the wire also can withdraw the tip of the wire

from its secure position in the distal pulmonary artery!

As a last alternative, partial inflation of the balloon with

the balloon tip positioned just proximal to the stent may

be enough to move the wire away from the edge of the

stent and “center” the tip of the balloon catheter in the

ves-sel/stent As the balloon is deflated slowly, the tip of the

balloon catheter and, hopefully, the balloon itself can be

advanced into the stent over the “centered” wire This

inflation of the balloon is used as a last resort since the

inflation eliminates the original smoother “factory fold”

of the balloon and may make the introduction of the rest of

the balloon into the stent impossible

Occasionally, no maneuver allows the reintroduction of

a sheath, catheter, or balloon back into a freshly implanted

stent without some movement of the stent If a stent

moves at all in its freshly implanted state, it can easily be

displaced! Even if the position of the implanted stent does

not “look or measure” perfectly, if the freshly implanted

stent moves even slightly with subsequent manipulations,

reintroduction of anything back into it should be

aban-doned at that time When the stent has been in place for

three to six months, it becomes fixed very securely into the

vessel wall and can safely be re-entered and re-dilated

during a subsequent catheterization

Once the re-dilation balloon has been introduced into

the stent by whichever method is successful, the larger

or high-pressure balloon is centered exactly within the

stent and inflated to its maximum pressure or diameter

to expand the stent to its final diameter The inflation/

deflation is repeated several times to ensure maximumexpansion of the stent in the previously stenosed area.After maximum inflation of the balloon within the stent,the balloon is deflated completely with maximum negat-ive pressure The negative pressure is released from theballoon lumen before withdrawing the balloon from the stent If a long sheath was used with the re-dilationballoon, if possible the sheath is re-advanced into andthrough the stent as the balloon is deflating, as describedpreviously

With all dilation and stent implant procedures, the

follow-up pressure measurements and selective angiograms

in the proximal vessel are performed before the deflatedballoon is withdrawn from the stent This allows furtherreinflation to correct for residual hemodynamic problems

or abnormalities seen on the angiogram or for the duction of the sheath into the stent Once satisfied with therepeat hemodynamics and the anatomic appearance, theballoon is withdrawn carefully out of the stent and intothe sheath or more proximal vessel and from there, out ofthe body When the balloon has been removed from thebody, an end-hole catheter is passed over the wire, and, ifpossible, to a position distal to the stent If it is not possible

reintro-to get it through the stent, the catheter is positioned justproximal to the stent The Super Stiff™ exchange wire iswithdrawn carefully through the catheter, out of the stent,and out of the body

“Front-loading” stent delivery

The “front-loading” stent delivery technique was oped because of repeated problems with hand-mountedstents sliding proximally off the balloons while they werebeing advanced through long delivery sheaths11 Front-loading of the stent eliminates this problem In addition,with the “front-loading” technique, a delivery sheath one,

devel-or even two, French sizes smaller can often be used fdevel-or thedelivery of a comparably sized stent/balloon For thefront-loading technique, an end-hole catheter and then aSuper Stiff™ guide wire are positioned exactly as for thestandard long sheath stent delivery The same extra effort

is used to position the catheter tip and, subsequently, thedistal end of the wire, as securely and as far distally to thestenosis in the vessel to be stented as possible

Technique for front-loading

The stent and balloon are prepared very differently for the

“front-loaded” delivery The long sheath that is used forfront-loaded stent delivery is chosen so that the balloon

with the stent mounted can just barely be accommodated

within the sheath This permits the use of a long sheath

that is at least one, if not two, French sizes smaller than the

long sheath that is used for a standard, through-the-sheath

delivery of the same balloon/stent While outside of the

body, the delivery balloon is passed from the proximal to

the distal end and completely through the long sheath

until the balloon is exposed entirely beyond the distal end

of the sheath The stent is mounted on the balloon while

the balloon extends out of the distal end of the sheath, but

otherwise, the stent is mounted exactly as for the

stand-ard, through-the-sheath delivery technique

Once the stent is mounted and tightly crimped on the

balloon, the balloon catheter with the mounted stent is

with-drawn into the distal end of the sheath The withdrawal into

a tight fitting sheath requires considerable “finger

com-pression” of the tip of each individual exposed strut at the

proximal end of the stent as each strut is withdrawn into

the sheath The balloon, stent, and catheter are withdrawn

into the distal end of the sheath until the entire stent

(on the balloon) is within the distal tip of the sheath, but at

the same time, the tip and the “shoulder” of the balloon,

which are distal to the stent, extend just beyond the distal

tip of the sheath The balloon is inflated very slightly

Since most of the balloon and all of the stent are within the

very tight fitting sheath, the inflation only expands the

exposed distal “shoulder” of the balloon, which extends

just outside of the tip of the sheath In this position, the

inflated distal tip of the balloon extending out of the tip

of the sheath forms a “dilator tip” for the sheath while

the “inflated” portion of the balloon, which is within the

sheath, helps to “fix” the relative positions of the balloon

and stent tightly against the inner diameter of the sheath

While religiously maintaining the distal position of the

previously positioned long wire, the original short sheath

used for the diagnostic catheterization and the positioning

of the delivery wire is removed over the wire The tract

into the vein is dilated to at least the diameter of the long

sheath containing the balloon/stent While the balloon

catheter and the long sheath are fixed together very tightly

by finger compression over the balloon/stent at the distal

end of the sheath and the balloon catheter and stent at the

proximal end of the sheath, the combination of the balloon

catheter with the stent mounted on the balloon, which is

positioned just within the tip of the long sheath, and the

long sheath all are advanced as one unit, over the wire,

and introduced through the skin subcutaneous tissues

and into the vessel The partially inflated balloon

extend-ing beyond the tip of the sheath acts as the “dilator tip”,

although it does not have as smooth an interface with the

sheath or as stiff a “dilating” tip as a regular dilator The

balloon catheter within the sheath does not provide as

rigid support for the shaft of the sheath as the standard

long dilator provides Once through the skin and into

the vessel, the combination balloon/catheter/sheath is

advanced together as one unit over the wire, through the

heart and to the lesion Very careful attention and a very

tight grip on the sheath along with the enclosed shaft of

the catheter are necessary to keep the balloon/stent/

sheath combination all fixed together in precisely the same

relationship while the combination is advanced throughthe vascular system and heart The introduction and

advancing of this combination requires at least two pairs

of “knowledgeable” hands! It is impossible for a singlecatheterizing physician to advance the sheath while at thesame time keeping the catheter and sheath fixed together

as one unit and maintaining the wire securely in place

The hands of the additional and knowledgeable operator

or assistant maintain the wire in position and the sheath and catheter fixed together while the primary operatoradvances the sheath/catheter combination This is themost difficult part of a “front-loaded” stent delivery

In addition to the difficulties in introducing the bination sheath/balloon/catheter/stent over the wireand through the skin and subcutaneous tissues, the front-loading delivery technique has several other verysignificant problems, which occur while the combination

com-is being advanced through the heart to the lesion These

problems are significant enough to prevent the techniquefrom being used more regularly The inflated tip of the

balloon extending out of the tip of the sheath does not

cre-ate a smooth “dilator” tip nor a smooth interface betweenthe surface of the balloon and the “lip” of the distal end ofthe sheath Often, when there are any curves in the course

to the lesion, a wide gap is created in this interface As thesheath/catheter/stent combination is advanced, the gap

or “lip” at the leading edge of the tip of the sheath maycatch on intravascular or intracardiac structures and pre-vent the sheath from advancing further

The inflated balloon within the distal end of the sheath

does not fix the balloon–sheath relationship together very

securely and, as a consequence, the balloon/stent/sheath

combination functions very poorly as a “single unit” Asthe combination balloon/stent/sheath is advanced overthe wire and through the heart, the balloon with the

mounted stent is very easily pushed out of the sheath Inadvertent displacement of the balloon/stent out of the

sheath opens the stent partially and precludes any furtheradvancing of the sheath or stent If the stent on the balloonadvances out of the sheath completely, it easily becomesentrapped in the intracardiac structures Conversely, the

sheath can be pushed forward over the stent/balloon, which,

effectively, pushes the stent/balloon back into the sheath.

When the stent/balloon/catheter is further back in thesheath and the tip of the balloon is away from the tip of thesheath, the balloon tip no longer extends beyond the tip ofthe sheath as the “dilator”, and the open tip of the sheathwithout any “dilator” creates a very blunt and sharp

“leading edge”, which prohibits the sheath from beingadvanced any further

When the balloon is inflated to a significantly higherpressure in order to prevent balloon/stent movement

within the sheath, the lumen of the balloon catheter as it

passes through the balloon is compressed by the pressure in

the balloon and, in turn, prohibits the movement of the

combined balloon/stent/sheath over the wire

Finally, the shaft of the balloon catheter within the

sheath does not provide the stiffness and support for

“pushing” the sheath compared to the true long dilator

As a consequence, this lack of “shaft” support of the

sheath results in kinks in the sheath, buckling of the

sheath, or even “accordioning” of the sheath on itself

when the sheath is advanced against any resistance This

precludes advancing the sheath any further and can result

in the stent/balloon being extruded out of the sheath

prematurely as the catheter alone is advanced beyond a

stuck sheath which “shrinks” in length as it accordions

The multiple disadvantages of the front-loading technique

outweigh most advantages over the standard long sheath

delivery technique The front-loading technique is used

only when the standard delivery technique through a

pre-positioned long sheath has failed several times

When a front-loaded stent can be advanced all of the

way to the stenotic area, and as soon as the stent is

cen-tered in the lesion, the balloon, which is partially inflated

within the sheath, is deflated completely After the balloon

is deflated, this “loosens” the balloon/stent within the

sheath and removes any inflating pressure from the

bal-loon With the balloon deflated, the sheath is withdrawn

off the balloon/stent The remainder of the implant of the

stent is exactly as with the delivery technique through a

pre-positioned long sheath

“Ing” technique of front-loading

To overcome the “interface” problems between the tip of

the partially inflated balloon and the tip of the sheath,

Dr Frank Ing further refined the front-loading technique so

that a tip segment of the long dilator which came with the

long delivery sheath that is used to deliver the

stent/bal-loon, is used as the “dilator” during the sheath delivery12

This modification of the front-loading technique and

equipment eliminates the problems of the discrepancy

of the “balloon shoulder/tip of sheath” interface This

modification also allows P 108 or P 188 stents to be

mounted on even smaller balloons and delivered through

sheaths as small as 6- or 7-French! This, in turn, allows the

implant of stents which eventually can be expanded to the

final large adult diameters into the central vessels of infants

and small children The smaller sheaths used with this

modified technique follow the stiff wire to the lesion

with-out kinking better than the larger diameter sheaths The

shaft of the balloon catheter still does not create as much

support for the sheath as does the long dilator which

comes with the sheath and, as a consequence, extreme

care must be used in order not to bend or kink the sheath

as the combination smaller sheath/balloon catheter isadvanced through curves or bends within the cardiacstructures

The “Ing” modified, front-loaded device is advanced tothe lesion over a pre-positioned Super Stiff™ wire whichmust still be positioned far distal to the lesion with thesame care and attention used for the standard long sheathdelivery technique The stent mounting and the prepara-tion of the balloon catheter and sheath require more individual preparation by the operator than the more

“standard” front-loading technique

The long dilator is removed from the long sheath that is

to be used for the front-loaded delivery of the stent Likethe “standard” front-loading procedure, the ballooncatheter first is advanced from the proximal to the distalend and through the long sheath so that the entire balloon

is outside of the distal end of the sheath The distal end of

the long dilator is amputated 2–3 cm proximal to the tip of

the dilator The lumen of the dilator at the proximal end

of this cut-off segment of the dilator is significantly largerthan the “wire” lumen, which is at the very distal tip of the

dilator By rotating the proximal end of the shaft of this

cut-off segment of dilator in the “jet” of heat from an electric

“heat gun”, the proximal end of the cut-off segment ofdilator is softened While the proximal end of the segment

of dilator is still soft, the lumen of the softened proximalend of the segment of dilator is forced over the distal tip ofthe balloon catheter that is to be used for the delivery ofthe stent As the lumen of the amputated tip of the dilator

is forced over the tip of the balloon catheter, it is twisted or

“screwed” slightly onto the tip of the catheter distal to theballoon While the portion of the dilator is still “soft”, an

umbilical tape is tied tightly around the proximal portion of

the cut-off tip of the dilator, which is now positioned over

the very distal tip of the balloon catheter As the segment

of dilator cools with the tie around it, the wall of the off segment of dilator shrinks with a circumferential

cut-“groove” in it created by the tie around it The tion of the shrinking as it cools and the groove within thesegment of dilator which is over the tip of the ballooncatheter, forms a tight bond between the amputated dila-tor tip and the tip of the balloon catheter This processfixes the proximal end of the cut-off tip of the dilator

combina-against the distal shoulder of the balloon The dilator tip

now, essentially is a part of the balloon catheter

The stent is mounted on the balloon similarly to the viously described “front-loading” The stent is centered

pre-on the ballopre-on, making sure that the distal end of the stent

is behind the proximal end of the attached segment of thecut-off tip of the dilator The balloon, stent, and catheter,with the attached tip of the dilator, are withdrawn into

the sheath until the proximal, straight portion of the newly

attached segment of the tip of the dilator is withdrawn just within the tip of the sheath The withdrawal of the

balloon/stent into the sheath requires the same individual

crimping maneuvers over the tips of the struts of the stent

as it is withdrawn into the distal tip of the small sheath

Only the tip of the dilator, which is attached to the tip of

the balloon catheter, should extend out of the sheath This

tip of the original dilator for the long sheath re-creates

the original, smooth interface between the sheath and the

“dilator” The balloon is inflated partially within the

sheath to help secure the balloon/stent/catheter within

the sheath at that position With the balloon and stent

front-loaded they are delivered over the pre-positioned

stiff delivery wire exactly as with the previously described

front-load technique

Even with the “Ing” modification, it still is somewhat

difficult to maintain the front-loaded balloon/stent

pre-cisely together with the sheath as the combination is

advanced through the heart, and the shaft of the balloon

catheter still does not provide as strong support for the

advancing sheath as the true long dilator The biggest

dis-advantage to this technique, however, is that the “special

tips” for the balloon catheters must be “hand-made” and

“hand-mounted”, which requires some talent and

con-siderable additional time on the part of the operator

dur-ing each case

“Sheath-within-a-sheath” technique for the

pre-positioned long sheath delivery technique

The final sheath technique for stent delivery is a

combina-tion of the standard pre-posicombina-tioned long sheath delivery

and a front-loading delivery technique It is used in very

extenuating circumstances where a large stent must be

delivered through an extremely dilated heart or a very

tortuous course within the heart, and particularly to

lesions in the pulmonary arteries The

“sheath-within-a-sheath” technique usually is not used unless one or all of

the previous long sheath techniques have failed The

sheath-within-a-sheath technique is particularly useful

when there is a recurrent problem of the stent being

dis-placed off the delivery balloon as it is advanced to the

lesion through a long sheath An end-hole catheter and a

Super Stiff™ exchange guide wire (Medi-Tech, Boston

Scientific, Natick, MA) are pre-positioned across the lesion

and well into the vessel distal to the lesion as is

accom-plished with all of the other stent delivery techniques

With the sheath-within-a-sheath technique, the stent is

front-loaded into the smallest diameter long sheath that

will accommodate the desired stent when it is mounted

on the delivery balloon The front-loaded stent, balloon,

and sheath, in turn, are delivered to the lesion through

another, still larger diameter, pre-positioned, long sheath

This second, larger diameter sheath/dilator set must be

six to seven centimeters shorter than the smaller long sheath

into which the stent/balloon is front loaded and must be

large enough in its internal diameter to accommodate the outer

diameter of the smaller diameter long sheath in which theballoon/stent is front-loaded The outer extra-large longsheath is usually two French sizes larger than the longinner sheath The second, larger diameter, long sheath/dilator set is advanced over the pre-positioned SuperStiff™ wire and well past the lesion in the vessel The di-lator is removed from the extra-large sheath while main-taining the Super Stiff™ wire in its secure distal location.With this extra-large sheath in place, the dilator removedover the wire, and the sheath cleared of all air and clot, thesmaller diameter long sheath with the previously front-loaded balloon/stent/catheter is introduced into theproximal end of the pre-positioned, larger diameter longsheath The front-loaded balloon/stent/catheter/sheath

is advanced to the lesion through the larger long sheath The

front-loaded inner sheath/catheter prevents the stentfrom sliding on the balloon while it is being advancedthrough the outer sheath, while the outer larger sheathprovides a smooth course through the heart for the front-loaded balloon/sheath tip interface and obviates most ofthe problems of the pure front-loaded delivery The innersheath/balloon catheter combination provides some addi-tional support for the outer sheath to prevent kinking ofeither sheath This technique has always been successfulwhen the other techniques have failed The major disad-vantages of the sheath-within-a-sheath technique are theextra equipment necessary and the necessity of using theeven larger diameter outer sheath

Non-sheath delivery of stents

The delivery of stents which are currently available and

suitable for central vessels in congenital heart lesions has

been attempted without a long covering sheath, but

with-out consistent or reliable results Stents that are not

pre-mounted on balloons by the manufacturers cannot befixed securely on the balloons In addition, the J & JPalmaz™ stents (Johnson & Johnson, Warren, NJ) haveexposed, rigid ends, which protrude off the surface of the balloon when the balloon/stent passes through anycurve These tips of these stents frequently catch on intra-cardiac structures and can easily be pushed off the balloons

as the stent/balloon combination is advanced throughany curves in the vascular course to the lesion, especiallythrough the intracardiac structures Once the stent hasslipped off the balloon, the loose stent on the catheter shafthas sharp exposed ends When the catheter/balloon withthe loose hand-mounted stent is moved either forward

or backward, the stent can catch on intravascular tures and make removal difficult and dangerous to thepatient

struc-The Medium and “Large” Genesis™ stents (Johnson &

Johnson–Cordis Corp., Miami Lakes, FL) are pre-mounted

commercially and can be delivered safely without a sheath.

The walls of the balloons actually are “incorporated” into

the mesh of the stents and fix the balloon on the stent very

securely until the balloon is expanded Unfortunately,

these pre-mounted Genesis™ stents are only available on

balloons up to 9 mm in diameter, and the stents can be

expanded further only to a maximum diameter of 10–11 mm.

Although they are commercially available in the United

States as well as the rest of the world, they are not

applicable for use in any central vessels in humans except

possibly under very extenuating, life-threatening

situ-ations Although these stents are much easier to deliver, the

stents themselves create a future iatrogenic stenosis in

any vessel which eventually and normally will grow to a

diameter greater than 11–12 mm! The stenosis created by a

limited diameter of a stent unequivocally will require surgery

on the stent/vessel for relief of the iatrogenic stenosis

Larger, prototype Genesis XD™ stents (Johnson &

Johnson–Cordis Corp., Miami Lakes, FL) applicable

for use in central vessels were developed and produced

pre-mounted for experimental in vivo studies, and were

tested successfully in animals13 These prototype stents

are flexible and have closed cells at the ends producing a

smoother end to the stent Like the smaller diameter

ver-sions, these larger Genesis XD™ stents were “embedded”

very firmly on the balloons and could be delivered

through all varieties of tortuous vasculature without a

sheath and without dislodging the stent Unfortunately,

these pre-mounted, larger stents would be primarily for

congenital heart patients and, as a consequence, the

“small market” for these apparently does not “justify” the

commercial investment to produce them If the larger

Genesis XD™ stents ( Johnson & Johnson–Cordis Corp.,

Miami Lakes, FL) were made available pre-mounted,

these stents would obviate almost all of the difficulties

of stent delivery and make the implant of intravascular

stents in pediatric and congenital heart patients easier for

the operators and infinitely safer for the patients

Special circumstances for stents

Dilation of rigid stents to large diameters

As discussed earlier in this chapterain the discussions of

large balloonsawhen balloon expandable intravascular

stents are expanded on standard dilation balloons, the

ends of the balloons inflate first causing the ends of the

stents to flare out before the center of the stents even

begins to expand With large rigid stents, the flared ends

of the stent create an acute angle off the long axis of the

stent and vessel (see Figure 22.3) The ends of the stent, in

turn, project toward and into the walls of the vessel Theflaring of both ends of the rigid stent also creates an angle

at the center of the stent between the two flaring ends.With an initial expansion up to 10–12 mm in diameter,neither the angle of the distal tips against the walls of thevessel at the end of the stent nor the central angle appears

to be of any consequence However, with initial expansion

to larger diameters than 12 mm, the flared, distal ends

of the stent become almost perpendicular to the walls ofthe vessel When the ends of the stent are sharp, they diginto, and create a ring of small, punctate circumferential

“perforations” in, the vessel walls before the center of the stent begins to expand As the center of the stent begins

to expand, these embedded tips of the stent are pushedlinearly along the vessel wall creating small linear tears ateach puncture site In vessels surrounded by dense scartissue this probably is of no consequence, but in a “native”vessel these tears can be through the media and eventhrough the adventitia

With the initial expansion of rigid stents to diameters

greater than 12 mm, the angle created at the center of the

stent also becomes significant (see Figure 22.5) When the

angle at the center of the stent becomes more acute than

90°, it very likely cannot be “re-straightened” as the stent is

expanded to its full diameter and, in turn, leaves a “kink”

or “waist” in the expanded stent as further pressureagainst that area pushes against a perpendicular ridge of

struts at the center of the stent (see Figure 22.5).

Because of this phenomenon, when rigid stents areimplanted with initial diameters greater than 12 mm, theyare expanded sequentially, starting with a balloon lessthan 10 mm in diameter This is achieved in the case ofsmaller vessels or very tight stenoses by beginning theimplant with a single, smaller, delivery balloon In thelarger diameter vessels/stenoses, the initial implant isperformed using a Balloon In Balloon™ (BIB™) balloon(NuMED Inc., Hopkinton, NY), which allows sequentialexpansion and still allows fixation in a large vessel with alarger diameter stenosis

When a stent initially implanted at a very small meter, or when a residual small central “waist” is being re-dilated to a larger diameter, the re-dilation is performedincrementally with separate balloons which are increasedsequentially in diameter If there is a central waist in astent which is 10 mm or less in diameter, a full, furtherexpansion up to 15 or 18 mm expands the ends of the stentfirst and aggravates the central “waist”, possibly creating

dia-a kink in the center of the stent dia-and mdia-aking it impossible

to dilate it completely

Bifurcating stents

The primary indication for bifurcating stents is the ence of stenosis at, or very close to, the branch point or

pres-bifurcation of two or more significant vessels If a single

Palmaz™ P _ _ 8 or P _ _ 10 series stent (Johnson &

Johnson, Warren, NJ) is placed across the bifurcation or

branch, the flow to the vessel usually is not blocked, but

the physical access to the branching vessel will be blocked

(“jailed”) by the initial stent crossing the non-stented

branch, which, in turn, will eliminate any subsequent

access to that branch with a catheter Branch or bifurcating

vessels of any significance are stented with the branching

or bifurcating stents implanted simultaneously with the

stent in the main vessel Occasionally the orifice of the

bifurcating or adjacent branch vessel is wide open, but the

distal branches in that same vessel have significant

steno-sis which will need intervention either immediately or in

the future In that situation, the proximal, non-stenosed

branch must be protected with a stent implanted

simul-taneously and “bifurcating” with the primarily stented

vessel to “protect” the access into the non-stenosed more

proximal branch vessel

The implant of large stents in areas of bifurcation or

at the origin of large branch vessels, particularly in the

pulmonary arteries, is technically the most challenging

procedure performed by the pediatric interventional

car-diologist First, it involves the implant of two (or more)

stents simultaneously along with the use of three (or

more) simultaneous venous catheters The exact location

of the stenosis and the relation of the stenosis to the branch

or bifurcation must be defined very precisely The two

(or more) stents must be implanted simultaneously and

very precisely into their exact locations Unless very precise

implant techniques are used, the simultaneously implanted

and bifurcating stents can easily create a catastrophic

situation When simultaneous stents are to be implanted,

both branches are analyzed very carefully for the degree

of stenosis, the distance from the bifurcation to the

steno-sis, and the distance to any additional branch points

When implanting bifurcating stents simultaneously, it

is even more important to use balloons slightly shorter

than the stents which are being implanted Longer loons flare (“dumbbell”) the ends of each stent duringearly inflations much more than balloons that are slightlyshorter than the stent Flaring of the ends of the stents cre-ates the perpendicular radius of sharp tips of the struts atthe ends of the stents, particularly with the rigid, J & J™Palmaz™ stents When adjacent stents are implantedsimultaneously, these exposed extended sharp ends of thestruts very likely will puncture the adjacent balloon,which is expanding the second expanding stent

bal-When crossing stents are implanted, both stents should

be at least 3 cm long and the crossing points of the twostents should be at, or as close to, the center of each of thestents as possible At the same time, the proximal openends of both stents must be proximal enough in the moreproximal vessel to allow access and not be obstructed bythe side of the adjacent (crossing) stent (Figure 22.8)

If there is a relatively long area of stenosis in either of the vessels, the more proximal areas which include the

crossing points of the stents, are addressed with the initial

implant of the stents Although two stents implantedsimultaneously tend to support and fix each other inplace, each separate stent should be appropriate for thesize of the separate branch vessel in which it is implantedand be capable of fixing securely into the walls of that vessel on its own

Occasionally, one of the stents in a bifurcating or ing situation can be implanted without inflating and

cross-expanding the second balloon and stent simultaneously However, access to the branching vessel, in which the stent

is not being implanted (expanded) initially and

simultan-eously, must be “protected” before and during the implant

of the first stent in the other branch This “protection” of

the branch is achieved by delivering the wire and the

sheath/dilator to the other branch vessel before the first

stent is implanted The sheath/dilator is left in place in theside branch vessel during the entire implant of the initialstent in the first vessel

Figure 22.8 Crossing stents implanted in a bifurcating lesion: (a) stents implanted too far distallyAproximal ends of implanted stents overlap each other,

obstructing subsequent access into at least one of the bifurcating/branch vessels; (b) bifurcating stents implanted more proximally with stents “crossing” each other nearer their centers Proximal ends of stents extend into more central vessel and provide subsequent access to both branches.

This separate implant of the stents has the advantage

that there is no simultaneously inflated stent to puncture

the adjacent balloon during the inflation for the implant of

at least the first stent At the same time, when the second

stent is implanted in a position crossing or next to the

pre-viously implanted stent, the balloon in the first stent must be

inflated along with and during the expansion of the balloon

in the second vessel/stent in order to prevent the initial

stent from being crushed The expanded balloon within

the stent which is already implanted and expanded, helps

to “protect” the second balloon from the sharp ends of the

struts of the original stent and helps to prevent puncture

of the adjacent (second) balloon by these sharp tips of the

original stent The technique of implanting crossing or

bifurcating stents one at a time has the disadvantage of

not creating the support against the tissues provided by

the two expanded stents adjacent to (crossing) each other

when they are implanted into large vessels This is

particu-larly true when one of the adjacent, more proximal orifices

is not stenotic

When there is a bifurcation stenosis occurring distally

in association with an additional and contiguous more

prox-imal single stenosis in the main, feeding vessel (Figure 22.9),

management of the combined lesions with the implant of

intravascular stents becomes more complex Although it

is counterintuitive to implant a stent in the more

prox-imal vessel and then have to work through the freshly

implanted stent to implant more distal stents, the single

more proximal stenosis, in fact, must be addressed first before

the additional bifurcating stents are placed in the more

distal branching areas of stenosis!

To overcome these problems, the larger single stent,

which will be in the more central stenosis that is

prox-imal to the bifurcating stenosis, is implanted first

(Figure 22.10) Once the more central stent is secured, the

more distal branching stenotic vessels are cannulated

simultaneously through the more proximal stent with

two (or more) catheters and wires passed separately but

adjacent to each other through the proximal stent The two or more stents in the branching vessel are implanted

with the proximal ends of the bifurcating stents both planted and overlapping within the distal end of the more

im-proximal single stent (Figure 22.11)

When the more proximal stent is very secure, the distalbifurcation stenoses can be addressed immediately afterthe more proximal stent is implanted However, if there is

a question about the stability of the first stent, the distalbranch stenoses are addressed at a subsequent catheter-

ization Once the bifurcating stents are in place, any

sub-sequent dilation, of the single more proximal stent and/or

either one or both of the distal stents, must be performed

with the number of balloons equal to the number of themore peripheral, distal stents These balloons are alwaysinflated simultaneously with the proximal ends extendingback into the single proximal stent and the distal endsextending out of the proximal stent into each of thebranching stents/vessels

If two (or more), distal side-by-side or bifurcating stentsare implanted first, in order to dilate and also support themore proximal single vessel stenosis with “a stent” after

the two distal stents have already been implanted, two

side-by-side stents would have to be implanted in the more

proximal single vessel stenosis in order not to crush one of

Figure 22.9 Diagram of combined central proximal right pulmonary artery

stenosis along with distal bifurcating right branch pulmonary artery stenosis.

Figure 22.10 Single large stent implanted first in the single, more central

stenosis, which is proximal to the bifurcating stenosis in the same vessel.

Figure 22.11 Distal bifurcating stents implanted through (out of ) and in

tandem with the single more proximal stent.

the more distal stents! This would create (and

necessit-ates) a dual channel in the single vessel The dual channel

would have to extend as far proximally as any more

prox-imal stenosis in order to treat the stenosis with implanted

stents (Figure 22.12)

When there are dual stents and/or two stent orifices

adjacent to each other anywhere in a vessel which requires

dilating and/or the implant of an additional stent,

sepa-rate balloons must be inflated simultaneously in each of the

adjacent stents during any subsequent dilation of either of

these stents This of course holds true as well if there are

more than two adjacent stents (e.g in a trifurcating branch

stenosis!) Any dilation more proximal (with or without

stents) made with a single balloon that is adjacent to and

outside of a stent which is not being supported by a

sec-ond balloon in that stent, will crush the adjacent stent

that is not supported with an inflated balloon in it at the

bifurcation or where the stents are next to each other

(Fig-ure 22.13) Any balloon and/or catheter in the adjacent

but unprotected stent/vessel could be trapped outside of

the expanding new stent!

When a single, more central stent is implanted in a

lesion that is very short and immediately proximal to the

bifurcation stenoses, occasionally a “skirt technique”a

which was originally described for coronary lesionsais

used to implant the initial, proximal stent14 In order to

ensure dilation and support with a stent of the short more

proximal stenosis as well as to guarantee access to bothbranches of the distal bifurcation, and in order not to over-dilate either of the distal branches while implanting thesingle, much larger, more proximal stent, the proximal

stent is mounted on, delivered over, and implanted on two

separate, adjacent balloons within the single proximal stent A

stent is chosen that will expand the proximal vessel/stenosis to the desired diameter Then, the two smallerballoons, which together will expand the single stentenough to fill and open the proximal pulmonary artery

to the desired diameter, are chosen and “negativelyprepped” The two balloons are placed side by side withinthe single stent and the stent is compressed and crimped

tightly over the two balloons A single, larger diameter long

sheath is used that will accommodate the combined meter of the two balloons together with the single stentmounted over them The large, long, sheath/dilator set isintroduced and advanced over a Super Stiff™ wire which

dia-is positioned as far ddia-istally as possible into one of thestenotic branches The tip of the long sheath is positioneddistally in the stenosis in the proximal vessel where thisinitial stent, which will be delivered on the two balloons,

will be implanted The large, long sheath is advanced as far

distally as possible over the dilator/wire within the singleproximal vessel and just to the area of the bifurcationstenosis off the central vessel The long dilator and SuperStiff™ wire are removed, leaving the sheath in place

A small torque-controlled end-hole catheter, through

which the wire which will be used in one of the balloon

catheters on which the stent is mounted will pass, is duced into and advanced through the large, long sheath.From the tip of the long sheath, the catheter is manipu-lated into and far distally in one of the stenotic bifurca-tion branches off the more central artery Once the firstcatheter is securely in place, a second similar catheter isadvanced through the long sheath adjacent to the first

intro-catheter, manipulated and advanced distally into the other

stenotic branch of the bifurcation Two separate exchangelength wires, which the two balloons on which the stent ismounted will accommodate, are advanced through theseparate catheters and wedged into the respective separ-ate distal pulmonary artery branches The two cathetersare withdrawn over the separate wires and the two bal-loons which are compressed within the single stent are

introduced over the two side-by-side wires, into the large

long sheath and advanced as a single unit over the twowires and through the long sheath to the stenotic area ofthe more proximal pulmonary artery

It is imperative that the two separate end-hole cathetersand, in turn, the two separate wires are advanced initially

to the separate stenotic pulmonary artery bifurcating

branches through the single long sheath which was

posi-tioned initially in the more proximal pulmonary artery.This ensures that the two catheters, and in turn, the two

Figure 22.13 “Unprotected” stent in an adjacent vessel crushed by balloon

expanded in adjacent vessel.

Figure 22.12 Parallel tandem stents extended back into single proximal

channel.

wires are passing through the exact same course through

the heart and do not deviate separately around even a

single chorda!

As the stent and two balloons are advanced distally

from the tip of the sheath, which is positioned in the

prox-imal pulmonary artery, the tips of the two balloons, which

extend out of the single stent, follow the separate wires

into the separate bifurcating branches off the more central

single pulmonary artery By pushing the balloons/stent

forward as far as possible, the single stent becomes

posi-tioned immediately adjacent to the bifurcation, while at

the same time buttressed against, and straddling the two

branches equally The sheath is withdrawn proximally off

the two balloons/single stent, and with the wires and

bal-loon catheters pushed forward as firmly as possible, the

two balloons are inflated simultaneously This expands

the single stent into the proximal vessel with the distal end

of the stent “flared” like a “bi-legged skirt” toward the

two distal stenotic branches Any subsequent dilations or

stent implants in the proximal vessel or the branches are

performed with separately delivered, but simultaneously

inflated, balloons

Tandem stents

Tandem stents are frequently necessary in vessel stenoses

that are longer than the available stents or in curved

lesions in order to have the straight rigid stents conform

better to the contour of the vessel The use of tandem

stents is particularly important with the limited available

lengths and the lack of flexibility of the J & J™ Palmaz™

stents (Johnson & Johnson, Warren, NJ)

In the deployment of tandem stents, it is important that

no gap is left (or allowed to occur later) between adjacent

stents Alternatively, the adjacent ends of two stents that

are within the same vessel, should have a wide separation

between the approximated ends of the abutting stents at

the time of implant The exposed, rigid and sharp end of a

single stent, by itself, creates an irritation, which results in

a build-up of the intima The irritation of the vessel wall

between the apposing ends of two stents that are in close

approximation to each other, is aggravated by the

move-ment or bending of the vessel that occurs in the gap

between the two stents The vessel movement causes the

two apposing, sharp ends to “grind” the tissues between

them, resulting in very aggressive, localized, intimal

pro-liferation Intimal proliferation in these “gap” areas is one

of the few documented causes of significant re-stenosis

in the many pediatric/congenital lesions that have been

stented

At implant, the adjacent tandem stents are overlapped

by a minimum of 35 to 70% The degree of overlap depends

upon the type of stent, the expected implant diameter

of the stents, which effects the shrinkage in length of the

stents, and the age and expected growth of the patient and,

in turn, the future growth in length of the vessel When

P _ _ 8 stents are implanted in potentially large (15–18 mm

diameter) vessels, which, however, are small in diameter

at the time of implant, they are overlapped at least

60–70% This degree of overlap is necessary to prevent

separation of the stents as the stents shrink in length as

they expand and to allow for subsequent growth of the vessel in length P _ _ 8 stents shrink ~50% in length with

expansion to their largest diameters The newer ITI™stents (ev3, Plymouth, MN) shrink minimally in length

when expanded sequentially and do not require as much

overlap to allow for the initial shrinkage or for shrinkagelater with further dilation

When tandem stents of all types are implanted in small, but growing patients, the potential growth of the patient and length of the vessel must be taken into account and an

even greater overlap of the stents created at the time ofimplant None of the stents “elongate” after implant, and,

in fact, when stents are dilated further in diameter toaccommodate the growth of a vessel, most stents shrinkeven further in length with re-dilation! At the same time,the tissues elongate as well as increase in diameter withgrowth, which results in the adjacent, tandem stents,which have a fixed length and are fixed in the tissues of thewall of the vessel, separating from each other, even whenthere was a significant overlap at the time of implant.When there is insufficient overlap of the adjacent stents,the ends actually separate and create an area of extremeirritation and intimal proliferation between the ends of the stents As a consequence, when sufficient overlap ofadjacent tandem stents cannot be provided to allow for

the patient’s growth, it is better to leave a large gap of at

least 5–6 mm between the ends of the adjacent stents at the

time of the initial implant An additional stent can beimplanted between the original stents after several years,when the patient is re-catheterized and the original stentsare re-dilated

When the area of stenosis to be stented is in a curvedvessel, two, or more, overlapping, short rigid stentsshould be implanted in tandem around the curve, ratherthan one long, straight, rigid stent This is particularlyimportant with the J & J™ Palmaz™ stents A shorter stent

on a short balloon is easier to deliver and implant in acurved vessel and a series of overlapping, tandem, shortstents conforms better to the curvature of the vessel than asingle long stent A longer straight, rigid stent implanted

in a curved vessel not only does not conform to the

curva-ture of the vessel, but leaves the long, sharp ends of a rigidstent digging into the outer circumference of the curva-ture of the vessel wall at an acute angle The sharp ends ofthe stents implanted at an acute angle to the wall of a ves-

sel are another demonstrated cause of excessive intimal

proliferation and re-stenosis following stent implant in

congenital lesions with the longer J & J™ stents (Johnson

& Johnson, Warren, NJ)

If multiple tandem stents are anticipated, at the initial

implant of each of the earlier stents, the earlier stents

implanted are not expanded to their final maximum

diameter with their implant, but with their initial

expan-sion are expanded only enough to fix the stents in place

This smaller initial diameter of the earlier stents allows

several more millimeters of expansion with the implant of

each subsequent stent This, in turn, allows subsequent

stents to be implanted at a slightly larger diameter than

the original stents in order to ensure the fixation of each

additional stent as it is expanded into the same vessel The

stents which were implanted earlier and initially, are

expanded further and incrementally with the implant

of each additional stent Eventually the full diameter of

that particular vessel can be achieved after the entire

length of the tandem stents has been implanted, yet

with-out significant over-dilation of the particular vessel when

the initial stents have been implanted at smaller than final

diameters If, on the other hand, the first or earlier stents

are expanded to the full diameter of the vessel with their

implant, in order to “over-expand” the subsequent stents,

they must be expanded to a diameter slightly larger than

the vessel to secure the additional stent(s) in the vessel and

within the initial stents

When tandem stents are implanted in veins, the most

distal (in the direction of blood flow) stent is implanted first.

If the proximal (in the direction of blood flow) stent is

implanted first, stasis of blood flow occurs in the newly

created lumen within the stent (proximal in the flow to the

more distal stenosis) This blood, which is not flowing,

tends to clot before the more distal stents are implanted

and more adequate flow can be established through them

In the pulmonary arteries with pulsatile, more vigorous

flow, the opposite occurs The more proximal stent is

implanted first If the more distal area is opened with no

blood flow coming from the more proximal, still stenotic

vessel, the blood in the dilated pulmonary bed distal to the

obstruction stops and will thrombose

Recent developments in stents

There are some improvements in the stents and in

the delivery systems for peripheral vascular use, which

somewhat inadvertently have “trickled down” or been

modified for the pediatric and congenital arena Of the

hundreds of new stent designs and stent materials that

have been introduced in the past decade for use in adult

vascular diseases, several have applicability, although not

“approval”, for the pediatric and congenital population

The three “groups” of relatively new or “pending” stents

which already have promise for congenital lesions are the

Cheatham-Platinum™ (C-P™) stents (NuMED Inc., kinton, NY), the Mega™ and Maxi™ stents (Intra Thera-peutics Inc., St Paul, MN) and the Genesis XD™ stents( Johnson & Johnson–Cordis Corp., Miami Lakes, FL) All

Hop-of these have been discussed in some detail earlier in thischapter

The Cheatham-Platinum (C-P™) stent (NuMED Inc.,Hopkinton, NY) has had extensive use world wide (except

in the United States) for the standard congenital lesions

It is not available routinely in the United States It was the

first stent available in the much larger diameters, whichalso had some flexibility and had rounded ends for safeuse in larger lesions Because of its unique characteristicsand wide range of “available” and “custom” sizes, and itsavailability with an expandable “covering”, the C-P™stent has had some unique investigational and compas-sionate use applications throughout the world, includingeven in the US The most innovative of these uses is the

“re-building” or “creation” of “internal venous tunnels”with very large, long and covered C-P™ stents for the

“completion of the Fontan” in the catheterization tory This catheterization procedure, if perfected, couldreplace two major cardiac surgical procedures

labora-The Double Strut™ stent (Intra labora-Therapeutics Inc.,

St Paul, MN) was the first stent approved for “human use”

in the US which had both flexibility and a truly open-celldesign, which have considerable appeal for use in con-genital lesions Several newer stents from ITI™ are nowapproved for human use in the US and appear to be evenmore suitable for pediatric and congenital lesions TheMega™ and Maxi™ stents (ev3, Plymouth, MN) still havethe favorable open-cell design as the Double Strut™ stentbut are stronger and/or larger

The Genesis XD™ stent (Johnson & Johnson–CordisCorp., Miami Lakes, FL) is an apparent replacement (suc-cessor) for the Palmaz™ P _ _ 8 series of stents (Johnson

& Johnson–Cordis Corp., Miami Lakes, FL) The GenesisXD™ has some flexibility, smoother ends and a partiallyflexible design, all of which improves the ease and safety

of its use Even with the improvements in its design, the

Genesis XD™ appears to have retained the strength of the

P _ _ 8 stents The Genesis XD™ stent appears to fulfillmost of the criteria of an ideal stent for many of the central congenital heart vascular stenoses, although more clinicalexperience with it is necessary before too much compla-cency develops about the delivery of stents!

Stenting of the atrial septum

Standard intravascular stents are occasionally used tomaintain an opening in the atrial septum for the tempor-

ary, or sometimes even permanent, palliation of complex

congenital heart defects Often the septal openings created

by a balloon atrial septostomy (Chapters 13) or a blade

and balloon atrial septostomy (Chapter 14) spontaneously

shrink in diameter or even close completely Standard

intravascular stents can be placed in the atrial openings

to maintain their patency Stents with a restricted central

diameter are used to create openings, but with a restricted

flow in atrial baffles in “failed Fontan” patients These uses

of intravascular stents are covered in detail in Chapter 14

“Future” developments in intravascular

stents

Large flexible stents without sharp tips at the

ends

It should be possible with a few adjustments of the laser

cutter to produce an even larger version of the Genesis

XD™ stent comparable in size and strength to the Palmaz

P 4010 and P 5010 stents ( Johnson & Johnson–Cordis

Corp., Miami Lakes, FL) A larger stent with the smoother

ends and with the slight flexibility of the Genesis XD™

would improve the safety of the stents for use in the aorta

or any other very large vessel The smoother ends alone

probably would eliminate the aneurysms that develop

during the implant of stents in the aorta as a result of the

sharp tips of the rigid J & J™ stents Whether the

pedi-atric/congenital “market” is large or important enough

for the manufacturers to make this happen, still remains

to be seen Hopefully, the already available Maxi™ stent

(ev3, Plymouth, MN) will fulfill the same criteria or the

large C-P™ stents (NuMED Inc., Hopkinton, NY) will

become available in the US to provide this added safety

for these patients

Pre-mounted, flexible stents

A prototype, pre-mounted version of the Genesis XD™

stent (Johnson & Johnson–Cordis Corp., Miami Lakes, FL)

was mentioned earlier This pre-mounted stent

under-went in vivo animal tests in early 200113 The pre-mounting

of these stents, like the other Genesis™ stents, is unique,

with the stent almost “incorporated” into the surface of the

balloon This pre-mounting along with the “smoother”

ends of these stents allowed the Genesis XD™ stents to be

delivered safely without the protection of a long sheath,

even when passing through the right heart and through

very tortuous vessels, and without the stent catching on

intravascular structures or being dislodged from the

bal-loon This very secure type of pre-mounting requires a

great deal of collaboration between the manufacturers of

both balloons and stents

The commercial availability of the larger pre-mounted

intravascular stents would make the implant of stents for

all of the pediatric and congenital heart patients easier and infinitely safer At the same time, pre-mounted stents initially would increase the cost of the procedure

significantly When stents that are not pre-mounted are

used, a single stent is suitable for use in many differentlesions and vessels with many different diameters Theseparate stent merely is mounted on the particular dia-meter balloon, which is applicable to the particular lesion

For the most part, the balloons that are used to implant

the intravascular stents are already in the inventory of the catheterization laboratory for the balloon dilation of

vessels and valves However, when using pre-mounted

stents, an inventory of a full range of each size of the mounted stent/balloon combination would be necessaryand the balloons with the pre-mounted stents would not

pre-be useable for other angioplasties without stent implant.Eventually, the costs of the procedures would “even out”,with less time required for the preparation and deliveryprocedure for the stents, less loss of balloons and stentsfrom stent slippage or balloon rupture/entrapment, andcertainly less time used as a consequence of the signi-ficantly worse complications now encountered with some

of the “hand-mounted” stents

Unfortunately, the major (and almost only!)

applica-tions for the larger pre-mounted stents are for pediatric/

congenital heart lesions As such and in the environment of

the US FDA, which does not recognize any stent for

pedi-atric or congenital heart use, this population does not represent a market, much less a profitable market, andcertainly not an area for future development, for Johnson

& Johnson–Cordis™ or, so far, for any other stent facturers to pursue specifically for this use

manu-Covered stents

There is considerable interest and ongoing development

of “covered stents” for the exclusion of aortic aneurysms

in atherosclerotic adults Covered stents have been usedoccasionally on a compassionate basis for emergency

“bail-out” in a few unique pediatric/congenital patients.The early covered stents that were used in congenitalpatients were hand-made by wrapping a “sleeve” of fabric or freshly harvested vein over or around a non-expanded stent The sleeve of covering material had the

same diameter as the desired final diameter of the vessel

that was being stented The sleeve of fabric or tissue wasattached to the stent by several sutures and the stent withthe covering sleeve was mounted on a balloon The com-bination was compressed and delivered through a sheathsimilar to the delivery of other balloon-expandable stents.These hand-made stents required a significantly largerintroductory sheath than the stent/balloon alone Whenthe stent expands, the covering sleeve expands and/orunravels and creates an “impervious” channel in the area

which is “covered” by the sleeve Hand fabrication of

these covered stents was tedious and very time

consum-ing and, of equal or more importance, the end product

was very unpredictable and imprecise

Eventually, new modifications with the covering

material built into, or onto, the stents were developed

and a variety of covered stents now are manufactured

and are available commercially for the adult market

(Manufacturers include: WALLGRAFT-Medi-Tech, Boston

Scientific, Natick, MA; JoStent-Jomed Implantate, GMH,

Rangendingen, Germany; Zenith-Cook Inc.,

Blooming-ton, IN and Excluder-W L Gore & Associates, Flagstaff,

AZ) These covered stents are for adult vascular use and

for use predominantly outside of the US Simultaneously,

more needs are arising for covered stents in congenital

heart lesions

Covered stents for use in congenital patients have even

more stringent limitations than standard stents Besides

the lack of availability for congenital use, the major

prob-lem for the use of covered stents in many congenital

patients is the subsequent growth of the patients and

ves-sels There is one oral communication which suggests that

some expandable polytetrafluoroethylene (ePTFE)

cov-ered stents can be dilated further in order to

accommod-ate the growth of a patient even several years after their

implant Until the single observation can be duplicated

and demonstrated to be reproducible in further animal or

human trials, this observation cannot be taken for granted

for all patients and types of stents/coverings Certainly, a

non-stretchable “covering” or fabric material over a stent,

which is similar to a circumferential prosthetic conduit,

cannot expand beyond the manufactured maximum

diameter of the material, particularly after there has been

tissue ingrowth into the covering/fabric This type of

cov-ered stent, in turn, would create a fixed maximum diameter

for that vessel, which is fixed by the diameter of the

cover-ing of the stent at the time of implant Until new

mater-ials/designs are available that can definitely be dilated

further once the covered stent has been in place for many

months, covered stents should be used only in patients

who have reached adult size, or in extremely extenuating,

life-threatening, circumstances

The covered stents which have been or currently are

being used in pediatric/congenital lesions, are those

which are available for adult peripheral vascular lesions

and, for the most part, have been used in isolated,

“emerg-ency bail-out” situations The first uses of covered stents

were for the control of acute tears in vessels Originally,

these were tears in smaller vessels (coronary arteries),

and usually the tears were iatrogenic following balloon

dilations Subsequently, the same concept was used for

the occlusion of degenerative tears and aneurysms of

the aorta There are at present extensive developments

and multiple clinical trials for the treatment of aortic

aneurysms in adults with covered stents With favorableoutcome of these trials and newer developments in thecovered stents, covered stents eventually will be moreapplicable to, and more readily available for, congenitallesions

There already has been a sporadic use of covered stents

in pediatric/congenital heart lesions for the repair ofacute tears in vessels, which occurred during balloon dila-tion procedures This currently involves the problem

of the necessary individual, “hand” preparation of the

covered stent during such an emergencyawhich is

time-consuming and somewhat inconsistent The ian approval or off-label availability of a commerciallymanufactured, more sophisticated covered stent in mul-tiple sizes would make this application more effective,more consistent and, again, much safer and even life-saving in acute catastrophic emergencies Covered stentsalso have an application for the occlusion of “windowtype” systemic to pulmonary communications, particu-larly those arising from the ascending aorta or enteringinto difficult to reach locations in the more distal pul-monary arteries (e.g unusual ductus and/or Pottsdescending aorta to left pulmonary artery shunts)15,16.However, if a covered stent is used for this purpose inmuch smaller patients, the covered stent must be capable

humanitar-of further dilation to accommodate for the patient’sgrowth! A few hand-made covered stents have been usedunder extenuating or emergency circumstances in con-genital patients for the purposeful occlusion for managingiatrogenic tears in vessels following balloon dilation ofbranch pulmonary arteries

Covered stents have been used for the treatment of tic tears that occur during the dilation of coarctations ofthe aorta, or even are suggested for use in the routinestenting of coarctation of the aorta17 A long covered stentpotentially obliterates the vasa-vasorum, intercostals

aor-and/or the spinal artery in the areas which can be included

under the stent and covered by the stent, with the ity of causing tissue ischemia or even paraplegia In theadult atherosclerotic, dissected aorta, where coveredstents are being used extensively, these critical side/branch vessels in general have not created a problem.Additionally, there is a real incidence of stent displace-ment during stent implants for coarctations of the aorta.Usually the errant stent is “re-implanted” in a smaller distal area of the aorta, and with a non-covered stent and

possibil-the knowledge that flow is preserved through possibil-the side of possibil-the

open stent, there is little concern when the stent crosses

side branches However, a covered stent which becomesdisplaced in the aorta, potentially would occlude criticalside branches which it crossed! In addition, there is thenecessity of very large introductory sheaths for hand-made and commercially available covered stents whichare currently available for the aorta

In spite of the lack of prospective or planned

commer-cial development in this area, the most innovative uses

of covered stents to date have been in congenital heart

lesions Covered stents were used to “rebuild” intra-atrial,

venous channels which were disrupted and leaking

significantly in several complex patients with single

ventricles who had undergone “Fontan” cavopulmonary

type single ventricle repairs18 There now are proposed,

surgical/interventionist (“hybrid”) collaborative trials

for the use of covered stents to “complete a Fontan”

proced-ures prospectively These developmental uses of covered

stents are described in more detail in Chapter 32

“Open-ring” stents

The use of intravascular stents in the central and

poten-tially large vessels still represents a problem in very young

or very small patients who have a very significant

poten-tial for further growth Small diameter, pre-mounted stents,

which can be delivered easily to the pulmonary arteries or

to other sites in very small infants, are readily available,

however, these small diameter stents cannot be dilated

sub-sequently to a size adequate to the diameter of even a small

adult central vessel Any stent with a small or limited

diameter, which cannot eventually be dilated to the adult

diameter of the vessel, represents an iatrogenic stenosis and

should not be used in these vessels This problem has been

overcome partially by the “Ing” modified, front-loading

delivery technique, which was described earlier in this

chapter and which allows the delivery of the current,

shorter, P 108 and P 188 stents through as small as

7-French sheaths These particular shorter stents can be

dilated to adult diameters; however, this is not the perfect

solution Even these stents and the necessary sheaths/

dilators are large and rigid relative to the size of a very

small infant Another area of potential future stent

develop-ment is a small stent, which either dissolves or can be

opened later to allow dilation to a diameter beyond the

nominal diameter of the original stent in order to allow

dilation of the particular vessel to the eventual diameter

of the adult vessel

Dr Ing developed a simple but very innovative

“open-ring” stent and validated its usefulness in one animal

study19 With his technique, one or two longitudinal cuts

were made along the entire length of standard P 154 or P

204 stents (Johnson & Johnson, Warren, NJ), which have a

maximal diameter of 10–11 mm This created a small stent,

which was split and “opened” longitudinally, completely

along one side, or with two longitudinal cuts on the

oppo-site sides of the stent, a “bi-valved” stent The incised

halves of the stent were reattached to each other with two

or three 6-0 resorbable sutures, which were placed along

each cut edge These “reattached” small diameter stents

were mounted on a balloon, delivered and implanted

easily through a 6-French sheath exactly as any other very

small stent These small, potentially “open” stents werethen dilated acutely up to 11 mm in diameter during their

implant without disruption of the sutures holding the two

halves together The resorbable sutures fixed the two gitudinal halves of the stent together securely enough toallow dilation to the full diameter of the particular stents.The expanded, sutured stent, when implanted, supportedthe dilated vessels at the widest diameter of the implantedstents, while the sutures maintained the edges of thestents together securely and long enough to allow securefixation of the stents into the tissues and to provide ad-equate support of the dilated vessel The sutures resorbedover 8 to 12 weeks Any time thereafter, further dilation ofthe vessel in the area of the stents separated the previouslyincised and sutured, longitudinal cut(s) in the stents,allowing further dilation well beyond the nominal limits

lon-of the original standard, smaller diameter stents Thisunrestricted dilation of the “opened” stents in the vessel is

sufficient to compensate for any subsequent growth of the

vessel The “open-ring” stent allows the delivery of a verysmall stent to very small central vessels in young infants

as small as 3–4 kilograms, while the “opened” stent

sub-sequently allows the vessel to be dilated eventually to an

adult diameter as the small stent splits

The stents which were utilized in the animal tion were prepared specifically for the study by the manufacturer (Johnson & Johnson, Warren, NJ) Themanufacturer performed the longitudinal cuts in thestents and polished and coated the cut edges in order

investiga-to resist corrosion similar investiga-to the surfaces and ends of allstents Unfortunately, the very small number of patientswho would require these stents prohibits a prospectivehuman study which could reach enough statisticalsignificance to satisfy the FDA, even if it lasted a century

As a consequence, these professionally cut and polishedstents are no longer produced for any use The only cur-rent alternative for the “Ing” open-ring stent is to “hand-cut” the stents, which would leave the edges rough andnot coated and, in turn, create some added unknowns for

a clinical trial Hand cutting in order to individually duce the “open-ring” stents also increases the difficultyand consistency of preparing each stent, and certainlywould decreases the safety of their use in these precariouspositions in these already critically ill infants

pro-Recently, the “open-ring” concept has reappeared inEurope as the “Growth Stent”20 The growth stent is lasercut and electro polished as a “bi-valved” stent withspecific, facing, “tongue and grove” areas where the twolongitudinal halves fit together in order to maintain theedges together more securely (QualiMed, Winsen/Luhe,Germany) The edges are held together with the sameresorbable sutures used by Dr Ing and are completely re-absorbed after 8 weeks In addition to its small size, this

stent has the advantages of having some open side cells

and “Omega” hinges between adjacent rows of cells, which

together give the stents considerable flexibility The

great-est advantage is that it is professionally manufactured and

commercially available at least outside of the US

Hopefully, with some enlightenment of the FDA

toward the humanitarian use of “congenital” devices in

adult patients, the precedence might extend to the very

small, unique and otherwise untreatable populations of

neonatal congenital heart patients Without resistance

from the FDA, it might be possible to import these unique

but rarely used stents or to persuade one or more of the US

stent manufacturers to make these or similar “open-ring”

stents available even for this commercially non-profitable

group of patients

Future stents

New intravascular stents continue to be developed

and improved for acquired vascular diseases in the adult

population Secondarily, but presently only fortuitously

and certainly not “officially”, these new stents become

available for congenital and pediatric heart patients

With some enlightenment of the FDA, hopefully some

Objective Performance Criteria (OPCs) can be agreed

upon between the professionals caring for these patients,

industry and the FDA which would allow not only

the approval of existing stents for congenital lesions, but

would permit and even encourage the development of

stents specifically for the pediatric/congenital population.

An alternative to the small open-ring stent might be a

small, but at the same time, a totally biodegradable stent

Biodegradable stents have been developed primarily with

the goal of preventing re-stenosis, but up until now, have

not proven satisfactory Such a small

resorbable/degrad-able stent, which is developed for larger coronary arteries,

could be ideal in order to “buy time” for severe stenosis of

major vessels in very small infants

Complications of stent implants

With the exception of the inappropriate use of a stent in a

particular location, the complications of intravascular

stents in the pediatric and congenital populations, are

almost all related to the implant procedures, and not to

the stents themselves Once successfully and accurately

implanted, and unlike the stents used in acquired adult

vascular diseases, there are very few late complications of

the stents themselves in pediatric/congenital patients

This is particularly true for the currently available, new

generation of stents Those late complications which have

occurred, are usually related more to specific peculiarities

of the underlying congenital lesions than to the stents

themselves Complications can occur during implantsinto any location in congenital lesions; however, implantsinto the pulmonary arteries (Chapter 23) are technicallymore challenging and result in more complications.The most significant complication of the stents them-selves is iatrogenic and occurs when an inappropriatestent is implanted in a particular vessel This occurs most

commonly when a small stent, which cannot be dilated to

the eventual adult diameter of the vessel, is implanted in agrowing patient This, in turn, will eventually result instenosis of the vessel that will be of equal or greatersignificance to the stenosis caused by the initial lesion Astenosis in a vessel due to a stent that is too small and can-

not be dilated any further, will require complex surgical

intervention to correct it To relieve the stenosis due to

a small stent, the entire segment of the vessel must beexcised or the entire length of the stent/vessel must bedivided and patched, whether any other surgery isrequired for that particular patient The use of a stent thatknowingly will eventually be too small for the vessel, isjustified only in life-threatening situations, and/or whenthe patient will require surgery in the area of the stent for

some other reasonafor example a “conduit” exchange

necessitated for growth

With the continued necessity of having to “make do”with the materials available rather than having thespecific stents and/or specific equipment designed forstent delivery in pediatric and congenital lesions, thephysician implanting stents in pediatric/congenitalpatients with complex lesions must anticipate a variety ofproblems with stent deployment and implant In turn, theoperator must be prepared to handle these so they remain

“adverse events” and do not result in permanent adversesequelae for the patient

The most important “treatment” of the complications ofstent implants, like all complications, is prevention! Tried,true and established delivery equipment and techniquesare used as often as possible Very careful attention must

be paid to all of the details of the procedures that havebeen demonstrated to be successful as well as safe for the implant of the stents Very careful observation of thecatheter, wire, sheath/dilator, balloon/stent, and finally,

the position of the stent, is essential at all stages of the

pro-cedure Taking “one step backward” and “regrouping” inorder to correct an erroneous position of any of the com-ponents of the system at any time during the implant pro-cedure helps to prevent complications or, at the very least,prevents repetition of most of the preceding procedure

“Short-cuts” in the techniques and changing to different,not previously tested equipment or techniques, frequentlyresult in problems with delivery or implant of the stent.New materials (wires, sheaths, balloons and even stents)and new techniques using unproven materials or newmaterials should be tested on animal models and then

have extensive, totally successful, human use with

ade-quate follow-up, before being advocated and published as

“successful” or certainly “routine”

With all complications that occur during stent implant,

it is extremely important (critical) to maintain the secure

position of the delivery wire through the stent in order to

facilitate a recovery from the misadventure

Specific complications of stent implants

Local vessel injury can and does occur at the introductory

sites in the vessels where the stents are introduced

Because of the usual large diameter of a stent mounted on

a dilation balloon, the introductory sheaths for the

deliv-ery of stents are necessarily large even in smaller patients

In spite of this, both arterial and venous complications

fol-lowing the implant of intravascular stents in pediatric

and congenital patients have been extremely rare Venous

damage at the location where the large sheath was

intro-duced can lead to total obstruction of the vein, but this

may go unnoticed until a subsequent cardiac

catheteriza-tion is attempted through the same vein

In spite of the very large sheaths required for the

balloon/stent combinations, particularly during the first

five years of the original stent implant protocol in

con-genital heart patients, there were remarkably few venous

occlusions found during the required routine

follow-up catheterizations of these patients This lack of venous

occlusions is attributed to the routine heparinization of

these patients during the procedure and to the meticulous

care of the entry sites during the sheath introduction,

dur-ing the procedure, and followdur-ing the removal of the large

sheaths All of these patients were placed on aspirin for six

months following the procedure, which also may have

contributed to the paucity of venous occlusive problems!

The experience with intravascular stents in systemic

arteries is relatively limited, but like the venous stents,

requires a large introductory sheath Like the venous

entry sites, the complications from the even larger sheaths

that are necessary for implanting stents in coarctation of

the aorta, have been very rare and probably also are

infre-quent because of the close, personal attention and care of

the arteries during the introduction of the sheath,

dur-ing the procedure, and after the removal of the sheath

from the artery

Although the majority of the central complications of

intravascular stents occur during stent implants, there are

a few problems which occur in or around previously

implanted stents during catheter manipulation or

addi-tional intervenaddi-tional procedures in vessels that were stented

previously Stents implanted even years earlier, can cause

problems during subsequent catheter manipulations

It is quite easy to trap a catheter or wire in an exposed,

side “cell” of a J & J™ Palmaz™ P _ _ 8 stent Catheters as

large as 8-French easily pass into and through the side,

fully “expanded diamond” opening of an expanded J & J™

Palmaz™ P _ _ 8 stent, but at the same time, even a verysmall catheter or wire can be difficult to withdraw fromthese same “diamond” spaces Because of the diamondconfiguration of the spaces, a catheter that is perpendicu-

lar to the wall of the stent passes easily into and through the center of the diamond space (Figure 22.14a) but,

when attempting to withdraw the catheter out of the diamond of the cell and if the catheter assumes even the slightest angle to the stent, the catheter is pulled to the side of the cell and wedged into a corner of the diamond and, in turn, becomes entrapped in the acute,sharp corner by the acute angles of the diamond (Fig-ure 22.14b) The more forcefully the catheter is pulled, the tighter the catheter is pulled into the acute angle

in the diamond and the tighter the catheter becomesentrapped This same mechanism of trapping occurs with smaller catheters and/or wires, which pass into theside cells of the stents more easily Prevention of this prob-lem is the most important treatment As a consequence,

great care should be taken in the manipulation of any catheter or wire in the area of, or back through, a previously

implanted stent

When a catheter becomes trapped in the side of a stent,however, recovery is possible A relatively stiff, curvedwire is used within the trapped catheter to free thecatheter A 3–4 cm long, 60–90° curve is formed on thestiff end of a standard 0.035″ or 0.038″ teflon-coated guidewire The curve on the stiff end of the teflon wire is formedoutside of the body and outside of the catheter Thecurved, stiff end of the wire is introduced into the proxi-mal end of the entrapped catheter and advanced to thearea where the catheter is trapped through the side hole ofthe stent The preformed curve of the wire within thecatheter, in turn, creates a new curve in the shaft of the

catheter at the location where it enters the side of the stent

and, in doing so, changes the angle of entrance of the

catheter through the side, diamond shaped opening in thestent to a more perpendicular orientation to the side of the stent The more perpendicular the catheter becomesrelative to the long axis of the stent, the more likely thecatheter will be to move to the center of the “diamond”and spring free of the stent The new curve formed on the

catheter by the wire eventually will be sufficient to change

the direction of the catheter as it passes into the side of thestent enough to loosen the catheter from the corner of the “diamond” in the stent wall While holding the wire

in this location, the catheter is withdrawn in very smallincrements while gently “jiggling” it out of the stent

If this does not accomplish the release, the position of the wire within the catheter or the curve in the wire ischanged until the catheter eventually becomes alignedperpendicularly and springs free

The same “change in the curve” of the catheter can be

accomplished using a 0.035″ or 0.038″ “active deflector

wire” within the trapped catheter The active deflector wire

is introduced into the trapped catheter as a straight wire

and advanced to the area where the catheter enters the

stent A “deflection” curve is formed gradually on the tip

of the wire (and, in turn, the catheter) As the catheter

curve changes, gentle traction along with slight “jiggling”

is applied to the catheter When there still is resistance to

withdrawal of the catheter, the amount of, and location of,

the curve are altered until eventually the catheter becomes

perpendicular to the “diamond”, loosens, and can be

withdrawn from the side of the stent

When a wire is entrapped in the side of a stent, any

attempt at a forceful withdrawal will unravel the spring

guide wire A torque-controlled, end-hole catheter with a

fairly rigid preformed curve on the tip is advanced over the

wire to the stent The change in the angle at which the

catheter/wire enters the stent, is usually enough to allow

withdrawal of the wire with minimal subsequent

manipu-lations and no force.

Even years after implant, any tip at the ends of the struts

of a J & J™ Palmaz™ stent, which continue to protrude

into the vessel, remain very sharp These sharp tips can

easily puncture balloons that are within or adjacent to the

implanted stent Occasionally a sharp tip of a strut of apreviously implanted stent bends and protrudes inwardtoward the lumen of the vessel/stent and, as a con-sequence, the sharp tip pointing toward the lumen willpuncture any subsequent balloon that is inflated withinthe same stent This problem of potential balloon punc-ture should always be anticipated in the presence of a pre-viously implanted stent An attempt is made to avoid thearea of protrusion when balloons are expanded adjacent

to the area where the stent protrudes When recognized,

a protruding tip occasionally can be pushed “flatter”against the wall of the stent/vessel with a large catheter orsheath, which is stiffened with a heavy, stiff wire within it

or with one of the kevlar covered balloons, which is lesslikely to puncture

When the tip of a strut is protruding at the end of a

previ-ously implanted stent, the protruding tips are “protected”

at least partially from adjacent balloons being inflated, by

the balloon that is being inflated within the original stentwith the protruding tip(s) in order to keep the originalstent from being distorted/crushed by the adjacent bal-loon This is particularly important when new stents arebeing implanted in the area of, or within, a previous stent.Puncture of the implanting balloon during the expan-sion of a stent results in the balloon being trapped within a

Figure 22.14 (a) Catheter passing straight (perpendicular) through side cells of stent; (b) catheter passing through side cell on an angle and trapped in side

cell of stent.

partially expanded stent, in which case, the balloon

can-not be inflated further nor deflated When a new stent is to

be implanted and there is even the possibility of a

protrud-ing portion of a previous stent in the area, a “test” inflation

with only the balloon is performed The balloon only is

inflated in the precise area where the new stent will be

implanted but without the new stent A punctured

bal-loon alone which is adjacent to a stent is an inconvenience,

while a punctured balloon within an unexpanded stent

can be a catastrophe

Previously implanted stents can be compressed, or

even crushed, by external pressures which occur in

an area/vessel adjacent to the vessel where the stent

is implanted Often this is unavoidable Compression of

stents occasionally occurs with stents that are positioned

adjacent to the aorta or the sternum in patients who have

had previous surgery The surgical scarring eliminates the

“mobility” of the adjacent vessels in relation to each other

These stents usually were placed in these particular

loca-tions to treat stenosis caused by the very same external

compression of the vessel When stents are used in these

areas, compression is expected or unavoidable Some of

the Double Strut LD™ stents (Intra Therapeutics Inc.,

St Paul, MN), which were implanted at diameters of 16 mm

or greater, rebounded or shrank from their implant

dia-meters acutely or collapsed partially over time without

being in areas known to be particularly vulnerable for

collapse from external pressure These particular stents

are no longer used in large-diameter vessels Stents which

do shrink or collapse can be treated with re-dilation along

with the implant of a second, but stronger, stent within the

collapsed stent

Stents can also be crushed from external, iatrogenic

forces This occurs in the operating room, when a vessel

containing the stent is “retracted” The iatrogenic

com-pression of a stent in the operating room can be prevented

when the surgeon is aware of the potential problem with

the stent, the problem is anticipated, and any external

force on the stent is avoided In the catheterization

lab-oratory, previously implanted stents can be compressed

when a vessel is being dilated or an additional stent is

being implanted in a vessel which is immediately adjacent

to the original vessel with a previously implanted stent

In order to prevent collapse of the original stent, a second

balloon should always be positioned in and inflated

within the original stent in order to “protect” the original

stent and prevent its compression by an expanding

bal-loon in an adjacent vessel Most stents which are

com-pressed only partially and remain in place, can be treated

by re-expansion with a balloon and the implant of an

additional stent within the original stent

The most significant potential late complication from an

implanted stent has been the erosion through the wall of an

adjacent structure In spite of the large number of stents

that have been implanted in positions adjacent to theaorta, fortunately, this is an extremely rare occurrence andseems to occur when a stent is implanted adjacent to, and compressed by, a large and markedly dilated aorta and only when there has been previous surgery on one orboth of the adjacent vessels The causes of the erosion inparticular patients are unexplained and this problemmust be considered in the face of a sudden deterioration

of a patient who has a stent implanted adjacent to a largedilated aorta

Surprisingly, even with the extensive manipulationrequired in very sick patients and the use of often verylarge, stiff catheters, wires and sheaths/dilators, therehave been very few reported adverse events or permanent

sequelae from the wire/catheter/sheath manipulations during

the delivery and implant of intravascular stents in atric/congenital heart patients This probably is due to theoverall extensive experience and the established tech-niques used by the majority of operators who are perform-ing intravascular stent implants in these patients

pedi-There are, at the same time, numerous, relatively mon problems which occur during the delivery andimplant of the stents themselves Displacement of thestents, at least to some degree, during their implant is

com-common in congenital lesions even when the current

optimal equipment and techniques are utilized When astent is displaced significantly, it becomes a complication.Displacement of a stent often is the result of not utilizingthe best techniques/equipment available and, in turn, isbest treated by prevention Inaccurate centering of thestent on the balloon or displacement of the stent off thecenter of the balloon during delivery causes the balloon

to inflate asymmetrically and, in turn, “milks” the stentforward or backward during the balloon inflation.Expanding a stent on a balloon which is too large in dia-

meter or too long for the vessel that is immediately adjacent

to the stenosis, can cause the balloon to be squeezed out ofthe narrower vessel and away from the area of stenosis.Any unusually narrowed area should be identified angio-graphically or with sizing balloons before the implant

is started and, in turn, avoided by starting with a smallerinitial balloon for the implant

Not using an extra stiff wire or poor positioning of the

wires during the delivery of stents, will compromise thecontrol over the position of the stent during implant.Inadequate distal wire position, either from softer wires,poor initial position or by loss of position during sheathand/or balloon/stent delivery is a major cause of stent

displacement During the stent expansion, the stiff portion

of a Super Stiff™ (Medi-Tech, Boston Scientific, Natick,

MA) wire must be positioned entirely across the lesion and

fixed securely across the precise area being stented with the

floppy tip and the transition zone of the wire advanced well

distal to and beyond the area of stenosis Also, the Super

Stiff™ wire is pushed forcefully into an “advanced”

posi-tion into the distal tissues beyond the balloon/stent so

that there is no “slack” in the course of the wire or balloon

catheter, and no to-and-fro movement of the wire or

bal-loon catheter is possible When the wire and balbal-loon

catheter are maintained in this position, advancing the

wire alone, even minimally, pushes the balloon catheter

and the stent/balloon backwards over the wire! With the

wire so positioned, the position of the stent can be

con-trolled very preciselyaa minimal push on the balloon

catheter alone advances the balloon/stent further into the

vessel/lesion, while a minimal push on the wire

“with-draws” (pushes) the balloon/stent slightly backward in

the vessel/lesion, and a forward push on both the balloon

catheter and the wire fixes the stent/balloon securely in

position Finally, the balloon/stent is inflated slowly so

that the balloon/stent position can be adjusted or the

inflation can be stopped with any movement of the

balloon/stent relative to the lesion

Once the stent has been implanted with the initial

inflation, the stent still can be moved or displaced

acciden-tally by manipulations with a deflated balloon The

relat-ively rough surface of the deflated balloon can easily

become caught within open spaces (cells) of a freshly

implanted stent When any slight rotation or to-and-fro

movement of the balloon results in comparable

move-ment of the freshly implanted stent, the likelihood of

dis-lodging the stent becomes very high This occurs more

frequently when a balloon ruptures, but can also occur

with any of the deflated “angioplasty” balloons, which

have very rough, deflated profiles even when not

rup-tured Entrapments of the balloon in a stent owing to

bal-loon ruptures are more serious and are covered in detail in

subsequent paragraphs Entrapment of a rough but still

intact balloon for the most part is preventable or treatable

First, the choice of a balloon with a smoother profile for

the implant of the stent helps to prevent this Secondly,

always reintroducing the sheath into the stent over the

deflating balloon as the implanting balloon is being deflated

separates the rough surface of the balloon from the inner

surface of the stent and prevents the balloon from

becom-ing entrapped within the stent

In the situation where the sheath cannot be re-advanced

over the deflating balloon and the freshly implanted stent

moves every time the balloon is moved, the additional

angiographic catheter, which is already adjacent to the

stent, is used to “buttress” the stent while an attempt is

made at withdrawing the balloon from the stent A gentle

(25–30°) curve, which corresponds to the curve in the

ves-sel proximal to the stent, is formed at the transition portion

of a short floppy tipped, 0.035″ Super Stiff™ wire This wire

is introduced into the adjacent angiographic catheter and

advanced to the tip of the catheter The now “stiffened”

catheter is advanced against the exposed proximal end of

the stent As the catheter is pushed against the end of thestent, the balloon is “jiggled” gently and withdrawn care-fully out of the stent Occasionally the rounded end of the angiographic catheter will pass preferentially into the

stent (when not desired!) and will not catch securely

against the end of the stent In this situation, the graphic catheter is replaced with an end-hole catheter.The same stiff wire is introduced into, and advanced to

angio-just within the tip of the end-hole catheter to be used to

stiffen the end-hole catheter The “squared” hollow tipand the distal opening of the end-hole catheter definitelywill catch on, and, in turn, will tend to “buttress” againstthe end of the freshly implanted stent, supporting thestent enough to withdraw the balloon out of the stent.Balloon punctures, leaks or disruptions during stentimplants produce even more serious “events” and oftenresult in major or even permanent sequelae These prob-lems occur primarily (only?) with the J & J™ Palmaz™stents Balloon leaks and disruptions are a result of severaldifferent problems Both punctures and balloon ruptures/disruptions are more common with thin-walled dilationballoons and during stent implants into the pulmonaryarteries The punctures can be very tiny with minisculeleaks or, at the other extreme, can be massive as a result

of a total disruption of the balloon Both small leaks in balloons and disruptions of balloons create significantproblems during stent implants

The most common causes of balloon puncture are the

sharp points that occur as the distal ends of the struts ofthe J & J™ Palmaz™ stents The effects of the sharp tips areaccentuated by the “flare” created at the ends of the stents

when each end of the balloon expands significantly before

any of the stent itself begins to expand (described andillustrated previously in this chapter) The likelihood ofthis type of puncture is increased when the balloon which

is used for the implant is longer than the particular stent

and, in turn, extends significantly beyond the ends of thestent, or when the implanting balloon/stent is expanded

to a very large initial diameter with a single expansion of alarge balloon This combination results in the distal ends

of the balloon expanding almost completely before the

ends of the stent even begin to expand (see Figure 22.2) As

the balloon continues to expand ahead of the ends of thestent, the sharp tips of the struts of the stent are directed

into the expanding wall of the balloon These punctures

occur during the initial expansion of the ends of the stent

and can result in the majority of the stent not expanding

at all The incidence of this particular type of puncture is

decreased by using balloons that are shorter than the

length of the stent for the delivery of the stents, using loons that do not have long shoulders, and by using stentsthat do not have sharp tips at the ends

bal-Another potential reason for the puncture of a balloon

is when J & J™ Palmaz™ stents are implanted in curved

lesions This cause of puncture is somewhat similar to the

condition which occurs when the balloon for delivery of

the stent is too long for the stent When a balloon begins to

inflate in a curved location, the balloon expands very

asymmetrically and the concave surface of the balloon,

which extends beyond the end of the stent, is “folded”

over, and initially expands acutely against the end of the

straight stent This places the surface of the balloon

per-pendicularly against the pointed tips at the end of the

struts of the stent Again the problem is avoided, or at

least lessened, by using balloons shorter than the stent and

by using stents with “rounded” ends

When “bifurcating” J & J™ stents are implanted

simul-taneously, the flaring sharp tips of one of the stents can

easily puncture the balloon which is being inflated in the

adjacent stent This is particularly true as the balloons

inflate to large diameters and the flaring, sharp struts at

the ends of the stents develop a very acute angle off the

inflating balloon The remedy for this is to minimize or

prevent the flaring by using shorter balloons or to expand

each stent sequentially using separate, sequential balloons

or BIB™ balloons (NuMED Inc., Hopkinton, NY) for the

delivery of larger stents Using stents without sharp tips at

the ends of the struts probably will help to prevent this

problem

Occasionally a balloon is punctured while the stent is

being mounted onto the balloon or during any lengthwise

repositioning of the stent on the balloon These punctures

in the surface of the balloon are very minute openings,

which cannot be seen and can easily go unnoticed until an

attempt is made to expand the balloon/stent This type of

puncture is avoided by “opening” the stent slightly and

“flaring” one end of the stent with a dilator, before

intro-ducing the balloon into the stent during the mounting of

the stent and by very precise, meticulous, and gentle

introduction of the stent into the balloon If at all possible,

“repositioning” of the stent on the balloon is avoided by

the proper centering of the stent on the balloon initially

and before the stent is crimped on the balloon A tiny

puncture that cannot be seen, becomes apparent when the

balloon with the mounted stent is placed on strong

nega-tive pressure while the stent is being mounted/crimped

on the balloon With strong negative pressure, a tiny,

con-tinuous stream of bubbles appears in the fluid within the

syringe of the inflator A strong vacuum should always be

placed on a mounted stent/balloon to test for tiny leaks

before the stent/balloon is introduced into the patient

A small leak in the balloon during the implant of a stent

is indicated by the stent not expanding properly, if at all,

as fluid is delivered to the balloon as pressure is applied

slowly with the inflator Simultaneously, as the balloon

inflation is attempted, a faint “whiff” of contrast will

appear distally in the vessel where the stent is being

implanted This “free” contrast is very subtle and may not

be seen at all when there is a tiny leak These leaks in loons can be the beginning of a major crisis or, at the veryleast, a significant problem The management of this “cri-sis” depends upon at which stage in the expansion of thestent the leak occurs, when it is noted and, of course, themagnitude of the leak If there is a large leak due to a largetear in the balloon, the leak is more obvious, the problemusually is much more serious and there are fewer alternat-ives for recovery

bal-If the balloon is noted to have a tiny leak before the stent

even begins to expand, there occasionally can be an

effect-ive fairly simple remedy Stop the balloon inflation diately and apply negative pressure to the balloon Anattempt is made at withdrawing the balloon/stent care-fully back into the sheath Even when the stent does not

imme-expand at all, this usually is not possible and an alternative

recovery technique is used When the leak is first noticedafter the ends of the stent have started to expand and theends are expanded to a diameter just larger than thesheath, there are several choices for recovery The alterna-tives again depend upon the degree of expansion of thestent and the magnitude of the leak in the balloon In the presence of a very tiny “pin hole” or “puncture” leak

in the balloon where the ends of the stent have expandedvery slightly while the center stays collapsed and the stentotherwise stays in position, an attempt is made to furtherinflate and implant the stent in spite of the small leak.The further expansion of the stent is attempted byinflating the balloon/stent combination faster than the

injected fluid can leak from the tiny hole! A hard syringe with a capacity the same as the balloon is filled with normal

saline The saline has a much lower viscosity than the

diluted contrast and flows faster through the balloonlumen of the catheter The saline is injected into the bal-loon as rapidly, and with as much hand force, as possible.Usually, this expands the balloon with the stent at least alittle further An even more rapid inflation of the leakingdilation balloon can be accomplished by using a pressure(power) injector, which is used for the contrast injectionsfor angiograms, for the rapid inflation of the balloon! Thesyringe of the power injector is filled with a volume of nor-mal saline 1.5–2 times the capacity of the balloon Thisvolume is delivered into the balloon at 600 psi with thepower injector The very rapid injection usually dilates thestent further The increased dilation often is sufficient to

fix the stent at least loosely in place within the vessel andallows the removal of the punctured and now torn bal-

loon The rapid inflation with the injector usually ruptures

the balloon, necessitating some further tricks for

remov-ing the balloon after the stent has been expanded Usually

the rupture in the balloon is longitudinal and the balloonmaterial remains intact except for the tear

After the “power inflation” and slight further sion of the stent, the balloon, which now definitely is

expan-ruptured, is deflated as much as possible First an attempt

is made at advancing the sheath into the stent over the

ruptured balloon and withdrawing the balloon out of the

stent through the sheath This usually is not possible, in

which case, the long sheath and/or the adjacent catheter

is/are advanced against the proximal end of the stent to

“buttress” and help hold the stent in position while the

balloon catheter is withdrawn very carefully out of the

stent This often requires a relatively forceful withdrawal

to pull the balloon out of the stent and back into the

deliv-ery sheath If the ruptured balloon can be withdrawn out

of the stent but not into the sheath, the wire is maintained

in position and the balloon and sheath are withdrawn

completely out of the body All of this maneuvering is

observed almost continuously on fluoroscopy During

the withdrawal of the balloon, the balloon catheter is

rotated very slowly to try to “refold” the torn “wings” of

the balloon around the catheter This maneuver is very

delicate and can easily dislodge the stent in spite of the

buttressing with the sheath/catheter

If the original ruptured balloon cannot be withdrawn

out of a minimally expanded stent without dislodging the

stent, an attempt is made to expand the stent further

start-ing with a new, much smaller, low-profile balloon, which

is advanced within the stent adjacent to the ruptured

bal-loon over a separate wire through a separate introducer!

This obviously is a major undertaking The original,

addi-tional angiographic catheter is replaced with an end-hole

catheter, or if the second catheter was not in place, a small

end-hole catheter, which will accommodate a 0.035″ wire,

is introduced from a separate venous puncture and

manipulated into the involved pulmonary artery Using

torque-controlled wires, skill and patience, a wire and

then the second catheter is maneuvered into the partially

expanded stent, adjacent to the trapped, ruptured balloon

and completely through the stent into the more distal

ves-sel Once the catheter is distal to the stent, the end-hole

catheter is replaced with as stiff a wire as possible, which

will accommodate a new, small, very low-profile balloon

dilation catheter The diameter of the balloon must be

sufficient to expand the stent further but the deflated

bal-loon must be able to pass adjacent to the original balbal-loon

The very low-profile balloon is advanced/manipulated

over the wire and into the stent, next to the ruptured

bal-loon The new balloon is expanded within the stent (and

adjacent to the trapped, ruptured, original balloon) This

expands the stent further and helps to fix the stent more

securely in place in the vessel This first expansion/

fixation with the low-profile balloon usually is sufficient

to allow the withdrawal of the ruptured balloon

Occa-sionally, however, a second, even larger balloon may

have to be used in sequence and adjacent to the ruptured

balloon to expand the stent enough before the ruptured

balloon can be withdrawn safely and completely Using

sequentially larger balloons, the stent is expanded untilthe ruptured balloon can be removed, and eventually thedesired diameter of the stent is achieved Once the origi-nal, torn balloon has been removed, a new balloon of thesize necessary to expand the stent fully is introduced overthe original wire and into the stent to complete the expan-sion of the stent to the desired diameter

During all of these manipulations, there is nothing toprevent the stent from being displaced forward if pushed

by the balloon or a catheter entering it! When a stent doesdisplace distally, the wire still should be maintainedthrough the stent and in a very distal, secured position Ifthe stent is displaced forward (distal to the stenosis) andoff the original balloon during these maneuvers, a balloonthat is slightly larger than the diameter of the partiallyinflated stent is advanced over the wire, into and com-

pletely through the stent until at least the distal end of

the balloon extends beyond the distal end of the stent The

proximal end of the balloon will be positioned within the

distal end of the stent or rarely the entire balloon will be

totally distal to the stent The balloon is inflated slowly and

at low pressure, hopefully expanding the part of the

bal-loon that is distal and outside of the stent, and expanding

the balloon (only) to a diameter equal to the diameter of

the stent without expanding the stent at all In this way, the stent becomes “trapped” on the proximal catheter shaft or

actually on the proximal end of the balloon The catheter,balloon, and stent are withdrawn over the wire back intothe area of stenosis until the stent is against the “buttress-ing” edge of the long sheath or the second catheter Theoriginal delivery wire should remain fixed in its position

as far distally as possible during all of the maneuvers withthe balloon/stent/catheter With the stent maintained inplace by the tip of the long sheath or the tip of a secondcatheter, the balloon is slowly deflated partially whilesimultaneously withdrawing the balloon very carefully

further into the stent until it is centered within the stent.

This balloon/stent is then inflated in the lesion, in order tosecure the stent within the lesion at least partially Whilestill “buttressing” the proximal edge of the stent with thelong sheath, this balloon, which is smaller than the lesion,

is withdrawn carefully over the wire and replaced with alarger balloon that is sufficient to secure the stent firmly inthe lesion

Occasionally during some of these maneuvers, the

sheath actually passes over the balloon and enters, or even

passes completely through, the loose stent The sheath

within a loose stent is a “double-edged sword” The

rup-tured balloon certainly can be withdrawn more easilythrough and out of the stent with the stent “protected”from the balloon by the sheath However, the sheath

within or through the stent provides no support for

hold-ing (buttresshold-ing) the stent in its desired position If thepartially inflated diameter of the stent is not enough to

hold the stent against the wall of the stenosis, the stent

can easily move forward or backward in the vessel over the

sheath within the stent When the sheath passes into the

stent in this circumstance, the second catheter positioned

against the proximal end of the stent is absolutely essential

in order to buttress the stent and keep it from being pulled

back out of the lesion into a larger more central vessel!

With the stent maintained in this position with the second

catheter, a new, larger diameter balloon is advanced

through the sheath (and stent) and centered within the

stent While “buttressing” the stent in this location with

the second catheter, the sheath is withdrawn out of the

stent and off of the balloon The balloon is inflated to

expand and fix the stent in its proper location

If the stent moves forward (distally), and cannot be

“trapped” and withdrawn by a balloon passed completely

through it as just described, the stent is expanded and

fixed in the more distal location in the involved vessel

Even though this is not the originally desired position,

there is little, or no, consequence from implanting the

stent in a distal, normal vessel The major potential

prob-lem is that the distally displaced/implanted stent may

cross a significant, side or branching vessel when

ex-panded This usually can be avoided but, if it does occur,

is of little or no consequence in the more distal vessels

When the stent, which is not fixed in the vessel, does

move backward (proximally) from the lesion and over the

sheath which has passed within the stent, the situation

becomes more precarious Attempts at withdrawing the

sheath from within the stent usually aggravate the

situ-ation by withdrawing and displacing the stent still further

proximally along with the sheath This is another situation

where the second (or third) additional catheter(s), which

already are present in the vessel being stented, is/are

essen-tial! If the additional catheter is not in place or is not an

end-hole catheter, the manipulations with the long sheath

and loose stent are stopped immediately A separate,

preferably large French size, end-hole, catheter is

intro-duced into a vein and advanced to a position just proximal

to the stent in the involved vessel A slight (25–30°) curve

is placed on the stiff end of a standard 0.038″ teflon guide

wire The wire is advanced to just within the tip of the

end-hole catheter, which is positioned proximal to the stent in

the involved vessel The stiff end of the wire is used to

stiffen and provide more control over the “extra” catheter

The catheter, which is “reinforced” with the wire, is

advanced and manipulated until the tip of the catheter

“catches” against one of the ends of a strut at the proximal

end of the stent Because of its rounded distal tip, the

separ-ate angiographic catheter, which may have been in place

already, usually will not catch on, or allow a significant

push against, the end of the stent When the only additional

catheter is an angiographic catheter, it is replaced with

an end-hole catheter The “squared” end, along with the

opening of the end-hole catheter, usually catches the end

of the stent with minimal manipulations of the catheter

Occasionally the angle of the wire within the catheter must

be modified several times in order to accomplish this The

“stiffened” catheter against the end of the stent is used tostabilize the stent in position while the sheath is manipu-lated When there is any proximal displacement of thestent out of the lesion, the reinforced catheter is used toattempt to “push” the stent forward (distally) over thesheath and back into the precise lesion The catheter withthe stiff end of the wire within the catheter and both push-ing against the stent usually are sufficient to hold the stent

in place during further manipulations of the sheath.During all of these maneuvers, extra care is taken to main-

tain the position of the original delivery wire through, and

well distal to, the stent and balloon

Once the stent is supported, the original ruptured loon is withdrawn through the sheath and replaced with anew, larger diameter balloon and preferably a balloonshorter than the original balloon initially used to implantthe stent The new balloon is centered within the stentwhile the sheath still is within the stent While “holding”the stent with the additional venous catheter(s) and hold-ing the balloon in position over the wire within the stent,the sheath is withdrawn slowly and gently from withinthe stent and completely off the balloon until the sheathtip is just proximal to the balloon The stent may need to bepushed purposefully distally by the “holding” catheter

bal-as the sheath is being withdrawn Once the sheath isremoved, the balloon is expanded at low pressure and just enough to approximate the inside of the partiallyexpanded stent With the larger balloon expanded at lowpressure within the stent and before expanding the stentfurther, the balloon catheter can be used to help repositionthe stent An angiogram is performed to confirm the exactposition The stent is expanded in this position with thenew balloon

When a high-pressure, rapid inflation of a punctured

balloon in the stent does not expand the stent sufficiently

to fix the stent or to allow the removal of the balloon, theoriginal balloon must be extracted from the very min-imally expanded stent by alternative means The sheath isadvanced forward against the proximal end of the stentand used to “buttress” the stent as the balloon is with-drawn forcefully (hopefully intact!) If the sheath alone isnot rigid enough to hold the stent in place, the tip of anadditional end-hole catheter supported by a stiff wire, asdescribed above, is advanced against the end of the stentadjacent to the tip of the sheath During all of these manipu-lations, extra attention must be paid to maintaining thedelivery wire through the stent and in its very secure dis-

tal location By utilizing both the tip of the sheath and the

tip of a stiffened, extra catheter together against the imal end of the stent, the stent is held in place while the

prox-balloon is rotated and forcefully withdrawn from the

stent This maneuver usually is successful in removing the

balloon although it may distort the stent significantly or

further disrupt the balloon in the process If the stent is

distorted, the proximal end of the stent is reopened with

a very low-profile, very small, dilation balloon passed

over the wire and into the proximal end of the distorted

stent The low-profile balloon is advanced sequentially

through the stent and reinflated until the entire stent is

expanded to the diameter of the balloon

Once the original, ruptured balloon has been removed

from the non-expanded stent and the stent has been

opened even slightly, but is still held in place only by the

end of the sheath or the tip of the extra catheter, the

smaller balloon is replaced with a slightly larger diameter,

still low-profile, dilation balloon If possible, the balloons

that are used for the sequential dilations are made of a

thicker walled, tougher material even at the expense of the

low profile Eventually a large enough balloon is introduced

into the stent to fix the stent in place in the original lesion

Large tears or total disruptions of balloons occur during

stent implant They occur as an extension of a small

punc-ture or leak, but more commonly, are a consequence of

excessive pressure applied locally to the balloon or the use

of balloons which basically are unsatisfactory for stent

implant The management of longitudinal tears generally

is similar to the management of large punctures

Circum-ferential tears in the balloon can lead to displacement of

the distal part of the balloon and are more likely to

dis-lodge the stent during attempted removal of the balloon

All of the problems of balloon rupture and entrapment

during a stent implant are more common and are far more

serious when the involved stent is in a pulmonary artery

A bare, partially opened stent, particularly with expanded

ends, should never be withdrawn through the right

ven-tricle When the stent is displaced distally into a branch

pulmonary artery and cannot be withdrawn and secured

back into the original stenotic lesion, it is expanded and

fixed in the distal branch pulmonary artery distal to the

original stenosis as described above

If the stent, now with the new balloon within it, is

dis-placed proximally into the larger more proximal branch

pulmonary artery or even into the main pulmonary

artery, the first attempt is to re-advance the stent/balloon

combination over the wire and back into the original

stenotic site When the partially expanded stent cannot be

maneuvered back to the stenosed area, the next

alternat-ive is to reposition the proximally displaced stent into the

contralateral pulmonary artery, which in the presence of

unilateral branch pulmonary artery stenosis, usually is

larger The balloon/stent combination is withdrawn over

the wire, completely into the main pulmonary artery, and

the balloon is partially deflated but kept within the stent

It is imperative to maintain a secure wire position through

the errant stent to maintain at least partial control on thealignment of the stent in the pulmonary artery If the wire

is inadvertently withdrawn from within the stent, the stentwill become free floating and tumble around in the mainpulmonary artery or even back into the right ventricle(particularly in the presence of significant pulmonaryregurgitation) This makes recapture of the stent difficult,time consuming, or even impossible The deflated balloonremains partially reinflated in order to help fix and alignthe stent in the main pulmonary artery

In order to move the displaced stent from the main intothe contralateral pulmonary artery, a new, additional wire

must be passed through the stent and then positioned

securely in the contralateral pulmonary artery An tional end-hole catheter is introduced into another vein.This additional catheter is manipulated adjacent to theoriginal delivery wire and the partially deflated balloon

addi-and through the central lumen of the loose stent After it has passed completely through the true lumen of the errant stent, the new catheter is manipulated into the contralateral

pulmonary artery, far distally and into a large branch ofthat pulmonary artery with the use of torque-controlledwires or deflector wires A new Super Stiff™ wire isadvanced through the catheter and fixed in the contralat-eral pulmonary artery Once the new Super Stiff™ wire is

in a secure position through the stent and into the

contralat-eral pulmonary artery, the original balloon is deflated fully

and withdrawn from the stent and then the original Super

Stiff™ delivery wire is withdrawn from the originallesion, out of the stent and out of the body

Once the new stiff wire is secured through the stent inthe contralateral vessel and the original wire is with-drawn, a new balloon, which is slightly larger than thepartially expanded, loose stent, is introduced over the

new wire and into the stent The balloon is inflated at a low

pressure with the balloon centered or slightly distally

within the stent in order to fix the previously loose stent

on the balloon, but not to expand the stent further Withthe stent fixed on the balloon, the balloon/stent isadvanced into the larger contralateral pulmonary arteryover the wire The rounded tip of the balloon extendingdistally to the stent facilitates this maneuver When suc-cessfully maneuvered into the contralateral vessel, theballoon and stent are “wedged” into the most distal pos-sible part of the vessel and the balloon is expanded to itsmaximum diameter/pressure to fix the stent in place Inorder to fix the stent more securely in this vessel, it may benecessary to replace this balloon with a slightly larger bal-loon and repeat the inflation It usually is necessary, andcertainly is advisable, to secure the stent in this position by

“buttressing” the stent with the tip of the additional hole catheter during the exchange to a larger balloon.Once the original stent is fixed in this location, the balloonand wire are withdrawn and the implant of a stent into the

end-original lesion is restarted with the positioning of a new

wire through the lesion!

If the balloon/stent cannot be advanced into the

con-tralateral vessel, then significantly more serious

alternat-ives must be considered One possible solution is to dilate

and fix the balloon/stent in the main pulmonary artery

This usually is not possible because of the very large

diameters of the central pulmonary artery Only if all of

these maneuvers and positions for the stent have been

considered/tried and are not possible, is the withdrawal

of the stent over a balloon and out of the pulmonary

artery, through the right ventricle and back into the

infe-rior vena cava even considered There is absolutely no

totally safeway to withdraw an exposed, even minimally

expanded, stent/balloon through the right ventricle and

tricuspid valve If any parts of the ends of the struts of the

stent are elevated off the surface of the balloon when the

balloon is inflated within a stent, withdrawal should

never be considered

The withdrawal of a displaced, partially expanded

bal-loon/stent from the pulmonary to a more proximal

sys-temic vein may be considered in only two circumstances

The first is when the proximal end of the incompletely

expanded stent either still is within, or can be withdrawn

back into, the tip of the sheath, or at the very least, the

proximal end is not expanded at all on the balloon In that

circumstance, the proximal end of the stent forms a tight

fit and a “tapered trailing funnel” extending distally over

the ruptured balloon With this rare situation, an attempt

at withdrawing the combination stent, balloon and sheath

through the right ventricle is considered At the same

time, the consequences of the partially expanded balloon/

stent becoming entrapped in the right ventricle/tricuspid

valve apparatus must always be considered very seriously

and surgical support must be available immediately

The other circumstance when a withdrawal of the

exposed, partially expanded balloon/stent through the

right ventricle is attempted, is when the partially inflated

balloon fills the entire, partially expanded stent very

“snugly” with the stent fitting tightly on, and expanded

smoothly over the surface of the balloon There must be no

free or flared ends or struts of the stent extending off the

surface of the balloon proximally, and the balloon ends

should be expanded slightly larger in diameter than the

ends of the stent It is not advisable to consider

withdraw-ing a partially opened stent through the tricuspid valve if

there is even one sharp end of a strut or edge of the stent

extending away from the surface of the balloon

Even with a balloon expanded smoothly within a stent,

there is still a chance of a tip of the exposed stent becoming

“elevated” off the balloon and catching on the valve

appa-ratus! The combination of the inflated balloon filling the

partially expanded stent along with the sheath, is

care-fully withdrawn all together over the Super Stiff™ wire

which is still fixed across the lesion and into the far distalpulmonary artery Once the partially inflated balloon/stent combination is through the right ventricle (and tri-cuspid valve!), the combination is withdrawn until thestent can be fixed in a benign location more proximally inthe venous system (e.g the inferior vena cava or iliacvein) When the original stent has been fixed securely in aperipheral venous location, the implant of an additionalstent into the original location is reconsidered

If, before the original balloon ruptured, the stent wasexpanded too much for the stent to be withdrawn backinto the sheath but, at the same time, the balloon did notexpand the stent enough to allow removal of the balloon

by any of the previously described techniques, then thechoices depend more upon the location of the stent.Usually, in this circumstance, the ends of the stent areflared and the flared ends are the only part of the stentwhich expanded! Repeated attempts are made at intro-ducing the sheath into and through the stent over the rup-tured balloon or withdrawing the balloon forcefully fromthe stent supported against the end of the sheath and extrasupport catheter The risks of further attempts at catheterrecovery are significantly higher when the ruptured bal-loon cannot be withdrawn from the stent at all and, at thesame time, the stent is expanded partially off the surface

of the balloon

When a non-expanded stent with the entrapped balloon

is secure in the pulmonary artery and while the patient is

still in the catheterization laboratory, surgery can bescheduled and performed, on a less than “urgent” basis onthat same day, and the removal of the stent/balloon fromthe pulmonary artery can usually be performed withoutcardiopulmonary bypass If, on the other hand, thestent/balloon combination becomes entangled in the rightventricle/tricuspid valve during an attempt at with-drawal, the valve is both propped open and partiallyobstructed or there may be damage to the valve If the

stent over the balloon does become trapped within the right

ventricle, an attempt is made at withdrawing the deflatedballoon over the wire and out of the stent, leaving the stent in the right ventricle The stent alone does not causeobstruction to flow and occasionally the stent can begrasped and gently teased out of the ventricle21 If not,with the patient remaining stable, the patient can bescheduled for relatively elective surgery When the stentwith the balloon becomes trapped in the right ventricleand the balloon cannot be withdrawn from the stent, thepatient requires emergency surgery, which now must beperformed on cardiopulmonary bypass The alternative

of a referral for elective surgical removal of a partiallyexpanded stent on a ruptured balloon, which is positionedsecurely in a pulmonary artery and cannot be manipu-lated to a benign position in either pulmonary artery, is

prudent and always should be considered.

When a partially expanded stent on a ruptured balloon

is present in, or is withdrawn to, a position in the right

atrium or in either vena cava, and the balloon catheter is still

over the wire, the preferable approach is to implant the

stent securely in the inferior vena cava in a position away

from significant branching/side veins The wire within

the stent/balloon is maneuvered through the

stent/bal-loon, across the right atrium and into the opposite vena

cava This provides a guarantee that a stent that could

become totally free from the balloon, cannot embolize into

the right ventricle The original balloon is withdrawn

from the stent and a balloon large enough to expand and

fix the stent in the caudal inferior vena cava is advanced

over the wire and into the loose, partially expanded stent

The balloon is expanded at a very low pressure and just

enough to fill and “trap” the partially expanded stent

This usually results in the ends of the balloon expanding

slightly larger than the stent and, in turn, “covering” or

extending over the ends of the loose stent The balloon/

stent combination is withdrawn into the appropriate

loca-tion in the inferior vena cava and the balloon is inflated

fully, hopefully fixing the stent in that location in the cava

The alternative for a loose stent that is in the right

atrium or either cava, is to attempt removal of the

com-bination stent/balloon from the vascular system by a

catheter technique If a wire is not present through the

balloon catheter, an exchange length wire is advanced

through the balloon catheter, out of the tip of the catheter

and maneuvered as far as possible into the opposite vena

cava The partially expanded stent, which is stuck over the

balloon, potentially can be “re-compressed” over the

bal-loon with a snare and then withdrawn, at least to a

superficial vein, and partially if not completely into a large

sheath and out of the body A 20 mm Microvena™ snare

in a snare catheter is introduced through a separate very

large sheath The separate introductory site preferably is

into the same vessel and immediately adjacent to the

ori-ginal long sheath An alternative introductory site is

through the internal jugular vein when the original

bal-loon/stent was introduced from the femoral vein or, just

the opposite, from the femoral vein when the original

bal-loon/stent was introduced from the jugular approach

The snare catheter, which is introduced from the

separ-ate puncture site, is advanced with the enclosed snare

to a position immediately adjacent to the distal end of the

wire, which is in the opposite vena cava The snare is

opened in the opposite cava and maneuvered next to the

distal end of the wire, which more proximally is passing

through the balloon catheter/stent The guide wire within

the balloon catheter, which is still passing out of the tip

of the balloon catheter and across the atrium, is

with-drawn slowly until the tip of the wire is withwith-drawn just

proximal to the open snare This allows the open snare to

be maneuvered over the tip of the wire and eventually

maneuvered/withdrawn over the balloon catheter andaround the balloon/stent combination The wire is re-advanced out of the balloon catheter so that it again issecure in the opposite vena cava The wire passing com-pletely across the atrium provides a control or “safety net”

to ensure that a “dislodged” stent cannot embolize intothe right ventricle With the wire in this position, thesnare, which is over the stent, is tightened around the

balloon/stent until the stent begins to collapse slightly.

The snare is loosened and moved several millimeters up

or down the stent and the tightening is repeated Theentire process is repeated until the entire length of thestent has been re-compressed slightly over the balloon.The “squeezing” of the stent is performed in small incre-ments, moving along the length of the stent A very strongcompression in any one area can indent and distort thestent, which would prevent further uniform compression.This repeated “squeezing” process along the entirelength of the stent with the snare compresses the stentclose to its original, non-expanded diameter Even if thiscompression still does not allow the stent to be withdrawninto the original delivery sheath, it does allow the stent to

be withdrawn into a very peripheral vein near the ductory site into the vessel The snare is positioned

intro-around the most proximal part of the stent, and while

com-pressing the proximal end of the stent along with the rupted balloon with the snare, the combination of theballoon/stent, the original long sheath, the encirclingsnare and the adjacent snare catheter are withdrawn as farinto the introductory vein as possible, while all of the timekeeping the guide wire across the right atrium and intothe opposite vena cava The stent can usually be with-drawn to within a few millimeters of the introductory siteinto the vessel, where the balloon/stent should be palp-able beneath the skin just cephalad to the puncture site.The snare is released and an attempt is made at withdraw-ing the catheter/balloon/stent through the puncture site.When significant resistance is encountered, the balloon/stent on the catheter is removed through a small cut-downover the vessel

dis-In addition to the previously discussed complications ofstent implants, all of the complications of balloon dilationalone also occur during the implant of stents, but the usualcomplications associated with the balloons alone occur farless frequently Rupture of vessels is a complication of bal-loon dilation but rarely occurs during stent implant Withstent implants that are performed properly, the vessels aredilated only to the diameter of the adjacent normal vessel

and not over-dilated Dilation to the nominal vessel

dia-meter seldom ruptures a vessel

Hyperperfusion of dilated segments of the lung occurswith stent implants, and probably to a greater degree thanwith balloon dilation alone Once a vessel is opened to acertain diameter with a stent, no “recoil” or spasm of the

stented vessel can occur to reduce the flow to the vessel

distal to the dilated and stented area as opposed to a vessel

which undergoes dilation only Treatment of the

com-plications that are common to both balloon dilation

alone and balloon dilation with stents is the same for

both etiologies and is covered in Chapter 15 on “Balloon

DilationaGeneral” and Chapter 17 on “Balloon Dilation

of Branch Pulmonary Arteries”

Once implanted, intravascular stents have had

remark-ably few late complications in congenital heart patients

There usually is a less than one half to one mm of a normal

layer of protective neo-intima build-up within the lumen

of the stent This thin layer is present between the metal

struts as well as over the surface of the struts and does not

narrow the lumen of the larger vessels significantly This

usually occurs within three months, is smooth, and has

not been shown to accumulate further even over very

extended lengths of time for as long as a decade or more

A greater intimal build-up does occur in stents/vessels

when significant discrepancies remain in the diameters

of the lumens within the vessel and stent This atypical,

selective, intimal build-up does not narrow the vessel to a

diameter which is less than the narrowest adjacent

non-stented lumen or the narrowest area within the stent

which is present at the time of implant The selective

neo-intimal reaction is thought to be a consequence of the

excessive turbulence in the blood flow caused by the

vari-able diameters at the involved areas within the vessel The

turbulence results in an exaggeration of the normal

stimu-lus to neo-intima formation caused by the implanted stent

itself The extra build-up of intima tends to “streamline”

the vessel, narrowing the overall vessel to the narrowest

diameter that exists immediately postimplant, rather than

actually narrowing the vessel or stent lumen further This

neo-intima tends to create a vessel of uniform, smoother

diameter, which is equal in diameter throughout its length

to the narrowest contiguous area of the vessel/stent at the

time of implant

When a residual “waist” or narrowing persists within a

stent immediately after implant, the neo-intima within the

stent fills in the adjacent, wider area of the stent over time

This, again, “streamlines” or “smoothes” the entire lumen

to correspond to the narrowest residual diameter within

the stent immediately after implant This build-up of

intima has been interpreted as “re-stenosis”, but it does

not narrow, or re-stenose the vessel to a narrower diameter

than the narrowest diameter that was present at the time

of implant

Similarly, when a stent is over-expanded to a diameter

larger than the adjacent normal vessel during the initial

implant, the stent, over time, tends to work its way into, or

even through, the wall of the vessel As the stent migrates

into and through the wall of the vessel, the vessel wall

“heals behind” the expanding stent and grows back

within the stent to a diameter equal to that of the normal

adjacent vessel The over-expanded stent eventually

appears to rest on the outside of the vessel, and creates ameasurable distance from the lumen of the vessel to thestent Even though the stent appears to be outside of thevessel lumen, there have been no consequences of thisphenomenon This thickness of wall within the stent alsohas been misinterpreted as “re-stenosis” whereas, in fact,

the vessel again is “streamlining” and does not narrow to a

diameter that is less than that of the adjacent vessels Thisphenomenon appears to have no consequence, but can beavoided for the most part by not over-expanding a stent

beyond the diameter of the adjacent, non-stenosed vessel.

There are very rare, true “re-stenoses” in stentsimplanted in pediatric and congenital vascular lesions Inessentially all cases, however, when re-stenosis is seen,there is some unusual circumstance about the particularimplant or it is in a very unusual vessel or with some pecu-liarity of the tissues of the vessels themselves Re-stenosisdue to malpositioning of a stent or as a result of malalign-ment in the vessel is avoided by carefully positioning the

stent so that the stent aligns exactly in line with the lumen of

the vessel during implant In curved or angled vessels,this requires the use of multiple overlapping, shorter,rigid stents or the use of a “flexible” stent in order for theimplanted stent to conform to the curvature of the vessels

A long rigid stent placed in a curved vessel results in thesharp ends of the stent digging into the outer curvature ofthe vessel at an acute angle In this circumstance, there iscontinual irritation of the vessel by the sharp tips, and anexcessive intimal build-up will occur in those areas.There are several areas or vessels in congenital heartpatients where re-stenosis of the stented vessel occursalmost predictably The most frustrating of these “ves-sels” are the pulmonary veins Regardless of the type, theetiology or the location of stenosis in the pulmonary veins,re-stenosis recurs even after an apparently very success-ful dilation with a concomitant stent implant, and the re-stenosis recurs within a short period of time As of thiswriting there is no satisfactory definitive solution to thisparticular problem

The branch pulmonary arteries in patients after an rial switch procedure for transposition of the great arteriesrepresent another area after stent implant of more fre-quent re-stenosis Re-stenosis of these vessels after dila-tion with stent implants only appears to occur when theparticular pulmonary arteries are “stretched” longitudin-ally and excessively without sufficient freeing up of eachpulmonary vessel at each hilus as the pulmonary arteriesare pulled anterior to the aorta during a “Le Comp”maneuver When re-stenosis has occurred in these uniquepulmonary arteries after stent implants, it has beentreated successfully in all of the cases with re-dilation andfurther stent implants in any of the re-stenotic areas

arte-Stents placed in tandem, which do not overlap when

implanted or which separate a short distance from each

other later during longitudinal growth of the vessel, create

a “grinding” area between the ends of the two stents

When the ends of two stents are within one mm of each

other, very aggressive intimal build-up and stenosis

occurs between the stents This is avoided by creating

sufficient overlap at implant to prevent separation and to

allow for the growth of the vessel in length as well as

diameter The alternative is to leave a distance of at least

5–6 mm between the ends of the adjacent tandem stents

when they are implantedae.g when trying to avoid a

significant branch vessel which arises between or within

an area of stenosis

Stents implanted adjacent to strong external

compress-ing forces can be compressed or can even collapse For

example, a stent placed in a pulmonary artery directly

behind a large dilated aorta occasionally is compressed

into an ovoid cross sectional shape or even fractured

lon-gitudinally and collapsed The compression of the

pul-monary vessel often was at least part of the indication for

the stent to begin with and, in this circumstance, is hard to

avoid A compressed stent is treated by re-dilation with

the implant of additional stent(s) within the original

com-pressed stent

Stents within right ventricular to pulmonary artery

con-duits, which are situated between the sternum and the

muscular beating heart, frequently collapse or actually

fracture This almost is the expected outcome of stents

in this location The collapsed stent may remain in the

outflow tract or pieces of these stents break off and

embolize to the pulmonary arteries The distal pieces

appear to have no consequences even when left in place in

the distal pulmonary arteries With this knowledge about

stents in this location, the decision to implant a stent in

this location is made after weighing the temporary relief

of the obstruction, which can be achieved by the stent,

ver-sus the known, relatively frequent and early adverse

events from the collapse of stents there

There are several reports of “aneurysms” of the aorta

appearing acutely after the implant of large stents in

coarc-tations of the aorta In the reported cases, the stents

pre-sumably were implanted to their maximum diameters

on a single large balloon with a single inflation where a

circumferential ring of the sharp ends of the stents could

protrude perpendicularly toward (into!) the vessel wall

during the initial balloon expansion and before the center

of the stent even began to inflate These aneurysms are not

reported with stents implanted in the aorta with gradual

or sequential dilation of the stents The use of BIB™

balloons for sequential enlargement of these large

implants, and the availability of large stents with rounder

(smoother) ends, should obviate this complication

com-pletely The reported cases were addressed surgically

without further information about them but with no otherreported sequelae

Conclusion

The use of intravascular stents actually has reduced thecomplications of balloon dilation in all vessels Theadverse events and complications during delivery areminimized by close attention to the details of provendelivery techniques Hopefully many of the deliveryproblems have been or will be eliminated by improve-ments in the stents, balloon technology and delivery tech-niques Currently, even with the existing technology,intravascular stents are considered as the primary therapyfor vascular stenosis occurring in most congenital heartpatients

References

1 Mullins CE et al Implantation of balloon-expandable

intra-vascular grafts by catheterization in pulmonary arteries and

systemic veins Circulation 1988; 77(1): 188–199.

2 O’Laughlin MP et al Use of endovascular stents in congenital

heart disease Circulation 1991; 83(6): 1923–1939.

3 Driscoll DJ, Hesslein PS, and Mullins CE Congenital stenosis

of individual pulmonary veins: clinical spectrum and

unsuc-cessful treatment by transvenous balloon dilation Am J

monary artery stenosis Pediatr Cardiol 1997; 18(2): 101–106.

6 Shaffer KM et al Intravascular stents in congenital heart

dis-ease: short- and long-term results from a large single-center

experience J Am Coll Cardiol 1998; 31(3): 661–667.

7 Morrow WR et al Re-expansion of balloon-expandable stents

after growth J Am Coll Cardiol 1993; 22(7): 2007–2013.

8 McMahon CJ et al Redilation of endovascular stents in

con-genital heart disease: factors implicated in the development

of restenosis and neointimal proliferation J Am Coll Cardiol

2001; 38(2): 521–526.

9 Cheung YF et al Early and intermediate-term complications

of self-expanding stents limit their potential application in

children with congenital heart disease J Am Coll Cardiol 2000;

35(4): 1007–1015.

10 Recto MR et al A technique to prevent newly implanted stent

displacement during subsequent catheter and sheath

manipu-lation Catheter Cardiovasc Interv 2000; 49(3): 297–300.

11 Salazar OH et al Feasibility of a technique for branch monary artery stent implantation J Vasc Interv Radiol 1996;

pul-7(1): 41– 46.

12 Ing F et al A new delivery system for implantation of large

stents through small sheaths in infants and children with

branch pulmonary artery stenoses (Abstract) Cardiol Young

2000; 10 (Suppl): 152.

13 Forbes TJ et al The Genesis stent: A new low-profile stent

for use in infants, children, and adults with congenital

heart disease Catheter Cardiovasc Interv 2003; 59(3): 406–

414.

14 Kobayashi Y et al The skirt technique: A stenting technique

to treat a lesion immediately proximal to the bifurcation

(pseudobifurcation) Catheter Cardiovasc Interv 2000; 51(3):

347–351.

15 Preminger TJ, Lock JE, and Perry SB Traumatic

aortopul-monary window as a complication of pulaortopul-monary artery

balloon angioplasty: transcatheter occlusion with a covered

stent A case report Cathet Cardiovasc Diagn 1994; 31(4):

286–289.

16 Sadiq M, Malick NH, and Qureshi SA Simultaneous

treat-ment of native coarctation of the aorta combined with patent

ductus arteriosus using a covered stent Catheter Cardiovasc

Interv 2003; 59(3): 387–390.

17 Khan MS and Moore JW Treatment of abdominal aortic pseudoaneurysm with covered stents in a pediatric patient.

Catheter Cardiovasc Interv 2000; 50(4): 445–448.

18 Richens T et al Interventional treatment of lateral tunnel

dehiscence in a total cavopulmonary connection using a

bal-loon expandable covered stent Catheter Cardiovasc Interv

2000; 50(4): 449–451.

19 Ing F et al The new “open-ring” stent; evaluation in a swine

model Catheter Cardiovasc Interv 1998; 44: 109.

20 Ewert P et al Novel growth stent for the permanent

treat-ment of vessel stenosis in growing children: An experitreat-mental

study Catheter Cardiovasc Interv 2004; 62(4): 506–510.

21 Hoyer MH et al Transcatheter retrieval of an embolized Palmaz stent from the right ventricle of a child Cathet

Cardiovasc Diagn 1996; 39(3): 277–280.

The use of intravascular stents is accepted by most centers

as the safest, most effective and most definitive means of

treating branch pulmonary artery stenosis Surgical repair

of these lesions can relieve the stenosis, but surgery on

branch pulmonary lesions also directly or indirectly is a

major cause of branch pulmonary artery stenosis1 Balloon

dilation (angioplasty) of branch pulmonary stenosis alone,

at best, partially or temporarily relieves the obstructions2– 4,

while properly placed intravascular stents open the lesions

to the nominal diameter of the adjacent vessel, totally

relieve the gradient across the area of obstruction and, in

addition, appear to be the most cost effective treatment5,6

The delivery of intravascular stents to the branch

pul-monary arteries in complex pediatric and congenital heart

patients probably is the most difficult and challenging

procedure encountered by the pediatric or congenital

interventional cardiologist This results from the

combin-ation of the complex nature of the lesions along with the

“stagnation” in the development of the equipment

neces-sary for these procedures The delivery of almost all stents

to the pulmonary arteries first involves advancing the

large and stiff stents, which are hand-mounted on the

de-livery balloons, through major, often acute turns in the

course through the heart to the pulmonary arteries before

the target lesion even is reached Branch pulmonary artery

stenoses often have peculiar and acute angles of origin,

multiple areas of stenosis, large dilated or displaced main

pulmonary artery/right ventricular outflow tracts and

large dilated right atria and ventriclesaall of which

com-plicates the delivery of stents Most of the significant

branch pulmonary artery lesions are located in the larger,

more proximal areas of the pulmonary arteries and

require large, rigid stents with very strong walls which

must be capableof dilation to the eventual large diameters

of the adult central pulmonary arteries of that particular

patient All of these factors require the use of very large,

often stiff and complicated delivery systems The lems with the anatomy are compounded by the relativelycrude, and unnecessarily “antiquated”, expendable equip-ment, which is still the only equipment available for theimplant of stents in the larger or potentially larger branchpulmonary arteries in pediatric and congenital heartpatients

prob-The delivery and implant techniques described in thischapter are the techniques that are used for the delivery ofthe Palmaz™ P-308, P-188 and P-128 balloon expandable

“iliac” stents (Johnson & Johnson, Warren, NJ) to themajor branch pulmonary arteries7 These particular stentswere the original stents used for the central and branchpulmonary arteries and were the only stents available for this use in large vessels for the first decade of stentimplants in pediatric/congenital heart patients Therenow are several new stents with more favorable charac-teristics for delivery, which can be dilated to satisfactory

diameters of the adult central pulmonary arteries and, at

the same time, have sufficient wall strength to supportthese large vessels when they are dilated to diametersover 12 mm The characteristics, advantages and disad-vantages of these newer stents are discussed in detail inChapter 22

So far, all of the larger diameter stents which should beused in central vessels must be hand-mounted on thedelivery balloons, and most of the delivery and implanttechniques used for the original J & J,™ P _ _ 8 stents arestill used for the newer generation large stents Once thedelivery and implant of the original J & J™ P _ _ 8 stentsare mastered, the delivery of any of the new or improvedlarger stents is far easier and more straightforward Thesmaller, J & J™ P-204 “renal” stents (Johnson & Johnson,Warren, NJ) as well as the newer “Medium” and “Large”Genesis™ stents (Johnson & Johnson–Cordis Corp., MiamiLakes, FL) of similar diameters are currently available

and can be delivered far more easily using smaller delivery

sheaths and wires However, these smaller diameter

stents are only suitable for the smaller more peripheral

23 branch stenosis

branch pulmonary arteries and not acceptable for any

of the central pulmonary arteries or major, central

pul-monary artery branches

Pulmonary artery stent equipment and

delineation of the lesions

A biplane X-ray system with capabilities for compound

angulation of the X-ray tube is absolutely essential for the

implant of all but the simplest of pulmonary artery stents

In most cases, multiple branch pulmonary arteries are

involved, the lesions are in curved vessels, and the

sep-arate lesions occur in different vessels which arise at

markedly different angles from each other Multiple

simultaneous views are necessary, not only for the

im-plant of several stents at the same time, but during the

implant of each individual stent in order to visualize the

entire stent as well as the vessels adjacent to the target

lesion In addition to a biplane system, a high-quality,

biplane “freeze frame” replay system is required to

per-form pulmonary artery stent implants The number of

small “positioning” angiograms can be reduced by the

appropriate use of a good system to “road map” lesions

from a prior image

Currently, all stents are delivered to the pulmonary

arteries over Super Stiff™ wires and through long

sheaths Although it occasionally is possible to deliver the

stents that are currently available over a standard strength

wire, the softer wires provide much less control over the

stent/balloon and result in a much greater likelihood of

the stent being displaced away from a fixed location,

which, in turn, results in failure of the stent delivery/

implant Similarly, none of the current stents that are

suit-able for central branch pulmonary arteries are

pre-mounted Although these larger stents occasionally have

been delivered without a long sheath, there is a very high

likelihood of stent entrapment on right heart structures or

displacement off the balloon during the delivery to the

lesion Both the use of “standard” guide wires and the

delivery of stents without a long sheath increase the risks

of the procedure and decrease the likelihood of success of

delivering stents to the pulmonary arteries, and are not

recommended

For the delivery of a single stent to a branch pulmonary

artery, at least two veins are accessed at the beginning of

the procedure One venous access is used for the wire and

the sheath for the delivery of the stent and the second

venous access is for a separate catheter, which is used

for monitoring angiography When two stents are being

delivered simultaneously, a third venous line is accessed

for the additional angiographic catheter The best access

veins for delivery of stents to the pulmonary arteries

are the two separate femoral veins In larger children,

adolescents, and young adults when one femoral accesssite is obstructed and simultaneous stent implants are necessary, two venous lines can be “piggy-backed” into asingle femoral vein When “piggy-backing” sheaths in asingle vein, it is preferable, when at all possible, not toplace the two (or more) very large sheaths for stent deliv-ery in the same vein! As an alternative, a femoral vein and

an internal jugular vein are used for the introduction ofthe large delivery sheaths for the stent implants with thethird, smaller, “monitor/angiographic” catheter intro-duced “piggy-back” into the femoral vein A final altern-ative venous access for stent delivery to the pulmonaryartery is through the transhepatic approach, which isdescribed in detail in Chapter 4 This certainly provides a

“straight shot” to the right ventricle and right ventricularoutflow tract, and is preferable to any of the more cir-cuitous more peripheral veins The transhepatic route isnot a “standard” access route, but has been used success-fully for the introduction of large diameter sheaths

In the absence of access from either femoral vein, access

is obtained from the combination of an internal jugularvein and a hepatic vein for large sheath access while abrachial, axillary or subclavian vein can be used for theintroduction of the extra diagnostic/angiographic catheter.The more peripheral veins in the upper extremities usu-

ally are not suitable for stent delivery to the pulmonary

arteries The size of these peripheral veins usually is toosmall and, of more importance, the tortuous curvesencountered through the upper extremity venous chan-nels prevent the delivery of the rigid stents to the pul-monary arteries

The area of branch stenosis is identified and quantitatedaccurately from the pressure gradients and from the meas-urements on selective biplane pulmonary artery angio-graphy There is no one universal or specific angle or position which demonstrates any one particular area ofpulmonary branch stenosis the best The particular angles

of the X-ray tubes for each area of stenosis vary frompatient to patient and from lesion to lesion within thesame patient The view utilized for the primary “operat-ing” X-ray plane is the view in which the area of stenosis is

displayed maximally in its longest axis The second X-ray

plane is positioned to obtain the optimal view of anycrossing or branch vessels that arise off the target vessel

Frequently, several small selective angiograms into the

involved vessel, each time changing the angulation of theX-ray tubes slightly, are necessary to obtain the optimalviews These angles can be anywhere from straight AP,lateral, RAO and LAO projections, to any combination ofthese angles along with cranial or caudal angulation.When the two X-ray tubes are in the optimal positions

for the dilation and subsequent stent implant, a selective biplane angiogram is recorded in the area of the stenosis by injecting into the vessel being treated through the “extra”