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398 SECTION IV Pediatric Critical Care Cardiovascular patients In addition, the left AV valve may be severely regurgi tant 162 Inotropic support for the failing heart, afterload reduction for mitral r[.]

patients In addition, the left AV valve may be severely

regurgi-tant.162 Inotropic support for the failing heart, afterload reduction

for mitral regurgitation, and measures to decrease PVR may be

required perioperatively

Patients with trisomy 21 frequently have an associated

com-plete AV canal Measures to decrease PVR and the use of

pro-longed ventilatory support are often necessary because of their

tendency toward upper airway obstruction, sleep-disordered

breathing, and abnormal pulmonary vascular reactivity The large

tongue, hypotonia, upper airway obstruction, and difficult

vascu-lar access of these patients pose additional problems The most

frequent postoperative problems in patients with trisomy 21 are

residual VSDs, left AV valve insufficiency, and pulmonary

hyper-tension.163

Truncus Arteriosus Communis

Pathophysiology

With truncus arteriosus communis, the embryonic truncus fails

to septate normally into the two great arteries A single great

ar-tery leaves the heart and gives rise to the coronary, pulmonary,

and systemic arteries The truncus straddles a large VSD and

receives blood from both ventricles

Complete mixing of systemic and pulmonary venous blood in

the single great artery causes mild hypoxemia Both pulmonary

arteries usually originate from the ascending truncus, but

occa-sionally only a single PA originates from the common trunk; the

pulmonary artery orifice is seldom restrictive The resulting shunt

(simple) produces excessive pulmonary blood flow early in life as

the PVR decreases This pulmonary steal may decrease the systemic

blood flow; however, the presence of two functional ventricles

often prevents as significant a clinical manifestation as in patients

with true single ventricle Patients with truncus arteriosus may

have anatomically anomalous coronary origins; the addition of a

coronary runoff lesion may make them prone to early coronary

ischemia and subsequent ventricular compromise Children with

truncus arteriosus are at risk for developing early pulmonary

vas-cular obstructive disease, especially if delayed in their repair.164

Regurgitation of blood through the truncal valve may place an

additional volume load on the ventricles

Critical Care Management

Complete repair of this lesion should be performed early in the

neonate, before the pulmonary vascular resistance drops further,

resulting in clinical compromise.165 The VSD is closed with a

synthetic patch, and the pulmonary arteries are detached from the

truncus Continuity is established between the RV and the

pul-monary arteries with a valved conduit.166 The truncal valve may

require valvuloplasty if a significant amount of blood regurgitates

through it The presence of a dysplastic and moderately

regurgi-tant truncal valve poses additional challenges; most data suggest

that these patients are best served long term by cardiac

transplan-tation Pulmonary arterial banding or valve replacement may be

considered as an interim bridging strategy to this destination

Critical care management centers on control of pulmonary

blood flow and ventricular support Pulmonary blood flow may

increase further with anesthetic agents, hyperventilation,

alkalo-sis, and oxygen administration, resulting in hypotension and

acute ventricular failure If measures for increasing PVR do not

decrease pulmonary flow, temporary occlusion of one branch of

the pulmonary artery with a tourniquet limits pulmonary

flow and restores systemic perfusion pressure until CPB can be

instituted Because these patients are often in high-output CHF, myocardial depressants should be used with caution

Immediately after repair, the combination of persistent pulmo-nary arterial hypertension and RV failure can be fatal Hence, aggressive measures should be taken to support myocardial function and lower PVR adequately A residual VSD adds volume and pressure load on the ventricles and may have a devastating impact on the patient’s hemodynamics and oxygenation This should be suspected in patients who are not doing well postop-eratively, and any residual VSD should be repaired, if feasible Truncal valve regurgitation or stenosis may induce LV failure early during the postoperative period

Critical Care Management for Late Postoperative Care

Obstruction of the pulmonary conduit and the accompanying RV hypertension may occur early or late during the postoperative course Usually, the conduit is unable to support flow in the grow-ing child after several postoperative years Late development of truncal (aortic) valve regurgitation is possible For patients who underwent initial repair beyond late infancy, residual persistent pulmonary hypertension will most likely be a problem

Total Anomalous Pulmonary Venous Connection

Pathophysiology

Patients with TAPVC are cyanotic because their pulmonary veins connect to a systemic vein (complete mixing), and they have vary-ing degrees of pulmonary venous obstruction The venous con-nection may be supracardiac (e.g., to the SVC, innominate, or azygos vein), cardiac (e.g., to the coronary sinus), or infracardiac (e.g., to the hepatic veins, portal vein, or ductus venosus) Patients with this anomaly must have a patent foramen ovale or an ASD that allows blood flow to the left side of the heart

This anatomic arrangement provides complete mixing of all sys-temic and pulmonary venous blood in the right atrium Unless there

is significant stenosis of the pulmonary venous connection, most of this RA blood passes through the RV into the pulmonary artery, which increases pulmonary blood flow If pulmonary venous return

is significantly diminished due to obstruction, there is increased pulmonary venous congestion and decreased pulmonary blood flow

Critical Care Management

Patients with significant obstruction, typically those with PV that drain into subdiaphragmatic vessels, may be very ill with hypox-emia, severe pulmonary edema, and pulmonary artery hyperten-sion Resuscitation, including mechanical ventilation, PEEP, and inotropic support of the myocardium, is followed by early surgical intervention to relieve the pulmonary venous obstruction Al-though patients are hypoxemic, their primary pathology is caused

by obstructed venous return from the lungs Therapy that in-creases pulmonary blood flow (e.g., PGE1 or iNO) must be avoided Surgical repair of TAPVC requires attachment or redirec-tion of the pulmonary venous confluence to the left atrium Intraoperative and postoperative problems often are related to residual or recurrent stenosis of the pulmonary veins In patients who have severe and prolonged (often fetal) preoperative pulmonary venous obstruction, the pulmonary vascular bed is poorly reactive, reflected by highly pulmonary vascular resistance indices (PVRi) This elevation in PVRi results in high pulmonary artery pressures and poor RV function after bypass and during the early postopera-tive period Critical care management of these patients after comple-tion of the repair should emphasize inotropic support of the RV,

avoidance of myocardial depressant drugs, and minimization of

PVR Prolonged mechanical ventilation with gentle

hyperventila-tion and other postoperative therapy to decrease PVR are required

Inhaled NO has been particularly useful in this population,

pro-vided that there is no residual pulmonary vein obstruction.49

Critical Care Management for Late Postoperative Care

Other than the potential for late development of recurrent

pulmo-nary venous obstruction, these patients generally do well and have

good cardiovascular reserve once recovery from the surgery is

com-plete.167 The size of the pulmonary veins at birth may be a predictor

of late complications with recurrent pulmonary vein stenosis.168

Transposition of the Great Arteries

Pathophysiology

With transposition of the great arteries (d-TGA), the right

ventri-cle gives rise to the aorta Almost 50% of patients with this

anomaly have a VSD, and some have a variable degree of

subpul-monic stenosis Oxygenated pulmonary venous blood returns to

the left atrium and is recirculated to the pulmonary artery without

reaching the systemic circulation Similarly, systemic venous blood

returns to the RA and ventricle and is ejected into the aorta again

Obviously, this arrangement is compatible with life only for a few

circulation cycles unless there is some mixing of pulmonary and

systemic venous blood via a PDA or an opening in the atrial or

ventricular septum at birth The physiologic disturbance in these

patients is one of inadequate mixing of pulmonary and systemic

blood rather than one of inadequate pulmonary blood flow

Mixing of blood at the atrial level can be improved by balloon

atrial septostomy If dangerous levels of hypoxemia persist after

the septostomy and metabolic acidosis ensues, an infusion of

PGE1 can maintain the patency of ductus arteriosus, increase

pulmonary blood flow (by increasing left-to-right shunting across

the PDA), and thereby increase the volume of oxygenated blood

entering the left atrium The volume-overloaded LA is likely to

shunt part of its contents into the RA and thereby improve the

oxygen saturation of aortic blood Unlike other lesions, increased

left-to-right shunting of blood during anesthesia improves arterial

oxygen saturation before correction of the transposition

Depending on the particular anatomy and the presence of a

VSD or pulmonary stenosis, one of three corrective procedures is

used The intraoperative and postoperative problems encountered

differ with each type of procedure

Atrial Switch Procedure (Mustard and Senning)

An atrial-level partition is created with baffling to redirect

pulmo-nary venous blood across the TV to the RV and thus to the

aorta.169 Systemic venous (SVC and IVC) return is directed across

the atrial septum to the mitral valve, into the LV, and out the

pulmonary artery Although the pulmonary and systemic circuits

are then connected serially instead of in parallel, this arrangement

leaves the patient with a morphologic RV and TV in continuity

with the aorta Therefore, this ventricle must work against

sys-temic arterial pressure and resistance

One problem with atrial baffles is that they can obstruct

sys-temic and pulmonary venous return.170 When this occurs, the

patient manifests signs and symptoms of systemic venous

obstruc-tion, as evidenced by signs of systemic venous hypertension

When the pulmonary venous pathway is obstructed, pulmonary

venous hypertension may be manifested by respiratory failure,

poor gas exchange, and pulmonary edema Severe pulmonary

venous obstruction is manifested in the operating room by the presence of copious amounts of bloody fluid in the endotracheal tube, low cardiac output, and frequently poor oxygenation Re-sidual interatrial shunts also may cause intraoperative or postop-erative hypoxemia Long-term rhythm disturbances and the limi-tations of ventricular and AV valve function have made this operation nearly obsolete for standard transposition anatomy

Arterial Switch Operation (Jatene Procedure)

Because of the complications associated with atrial baffle proce-dures, Jatene and others explored whether anatomic correction of this lesion by dividing both great arteries and reattaching them to the opposite anatomically correct ventricle would improve sur-vival.171 , 172 This procedure requires excision and reimplantation of the coronary arteries to the neoaorta (formerly the proximal main pulmonary artery) LV mass decreases progressively after birth; thus, the ASO is done in the early (day 2 to 10 of life) neonatal period when the PVR (LV afterload) and LV pressure are high The success of the ASO depends on adequate conditioning of the LV and technical proficiency with the coronary transfer If the LV’s ability to tolerate the work required is misjudged, the child may develop severe LV failure postoperatively, necessitating significant vasoactive or mechanical support to maintain cardiac output In the instance of a late postnatal diagnosis of TGA with intact ven-tricular septum, the LV may require “reconditioning” by banding the pulmonary artery to encourage LV hypertrophy and hyperpla-sia, as well as a modified Blalock-Taussig shunt (BT shunt) to augment pulmonary blood flow.173 Although the ASO can often

be accomplished 1 week later, during this interval, these patients are often cyanotic and require considerable pharmacologic sup-port.174 In contrast, if the neonate has a nonrestrictive VSD, the

LV is accustomed to high systemic resistances and will tolerate the increased workload at any age Myocardial ischemia or infarction may occur after mobilization and reimplantation of the coronary arteries, especially if they are stretched or twisted Inotropic sup-port, maintenance of coronary perfusion pressures, control of heart rate, and treatment with vasodilators may be particularly useful, as in adult patients with myocardial ischemia Postoperative bleeding and tamponade occur more commonly with this opera-tion because of the presence of multiple arterial anastomoses

At experienced centers, mortality after neonatal repair of trans-position of the great arteries now is less than 3% and may be less than 2% for most anatomic arrangements of coronary arteries if the aortic arch is normal.175 Midterm and longer-term outcomes for the ASO are excellent, demonstrating a 25-year survival and freedom from reoperation rates of 96.7% and 75%, respec-tively.176 Alternative operations are reserved almost exclusively for patients with particularly difficult coronary anatomy177 , 178 or pul-monic (neoaortic) stenosis

Ventricular Switch (Rastelli Procedure)

This procedure can be used in TGA with VSD or double-outlet

RV when there is an unrestrictive outlet VSD and when coexist-ing pulmonary valve stenosis precludes a standard arterial switch operation The pulmonary valve is oversewn and the RV is con-nected to the pulmonary artery with a conduit.179

Complications of the Rastelli procedure include obstruction of

LV outflow as a result of the narrowing of the subaortic region by the VSD patch The conduit also may obstruct during or after the immediate postoperative period A small but significant inci-dence of heart block in these patients can be a difficult postopera-tive problem

Critical Care Management

Management of patients following an atrial switch procedure rests

on optimizing systemic oxygen delivery, monitoring for signs of

baffle obstruction, and control of atrial arrhythmias

Most patients post-ASO without a VSD have an unremarkable

postoperative course Persistent ventricular dysfunction heralded

by LA hypertension, hemodynamic instability, ventricular

arrhyth-mia, or evidence of ischemic changes should prompt an intensive

evaluation of the adequacy of the coronary anastomosis Any of

these perioperative issues or the unanticipated need for

extracorpo-real support necessitates immediate coronary evaluation and

revi-sion Special attention should be paid to postoperative bleeding,

given the extensive arterial suture lines

Patients with delayed intervention (either due to late

presenta-tion or comorbidities) usually will need to have a careful

assessment for possible LV insufficiency For these, an aggressive

strategy of systemic afterload reduction, deep sedation, and

mus-cle relaxation while expecting a more protracted ICU course is

often the norm Occasionally, these patients will benefit from the

use of ECLS or temporary LVAD support for retraining of the LV

in the postoperative course

Late Complications

Following atrial baffle, patients can be regarded as having a

physiologic or functional two-ventricle repair (i.e., the

morpho-logic LV is the pulmonary ventricle and the morphomorpho-logic RV

remains the systemic ventricle) Actuarial survival rates at 15 years

have been quoted to be up to 85%; however, significant long-term

functional deterioration is likely with increasing risk for right

heart failure, sudden death, and dysrhythmias.180 , 181 This

situa-tion is evidenced by systemic (right) ventricular dysfuncsitua-tion and

TV regurgitation long after the repair.182 These patients also are

prone to develop significant atrial dysrhythmias, including

supra-ventricular tachyarrhythmias and sick sinus syndrome later in

life.183

Virtually all coronary artery patterns are amenable to ASO No

particular pattern has been associated with late death A report of

coronary artery angiography in 366 patients following ASO

(me-dian age at follow-up, 7.9 years) revealed coronary artery stenosis

or occlusion in 3% of patients.184 Despite the angiographic

find-ings, evaluation with serial ECG, exercise testing, and wall-

motion abnormalities on echocardiography rarely demonstrate

evidence of ischemia.185

After repair, the native pulmonary valve becomes the neoaortic

valve A 30% incidence of trivial to mild aortic regurgitation has

been reported on intermediate-term follow-up, without

signifi-cant hemodynamic changes.186 Severe regurgitation is unusual

There appears to be a very low incidence of significant rhythm

disturbances after ASO.187 Supravalvar pulmonary AS was an

early complication but now is less common with surgical

tech-niques that extensively mobilize, augment, and reconstruct the

pulmonary arteries Supravalvar AS may develop but is rare

Assessment of myocardial performance using

echocardiogra-phy, cardiac catheterization, and exercise testing following ASO

has demonstrated function identical to that in age-matched

con-trols Based on the currently available clinical, functional, and

hemodynamic data, a patient who has undergone ASO with no

evidence of subsequent problems should be treated like any

pa-tient with a structurally normal heart when presenting for

noncar-diac surgery

Late complications of the Rastelli procedure include

progres-sive conduit obstruction and RV hypertension, residual VSDs,

and occasional subaortic obstruction from diversion of LV out-flow across the VSD to the aorta

Tetralogy of Fallot

Pathophysiology

The four anatomic features of TOF are VSD, RV outflow tract obstruction, overriding of the aorta, and RV hypertrophy There may be additional muscular VSDs, and obstruction of the pulmo-nary valve and main and branch pulmopulmo-nary arteries

Resistance to RV outflow forces systemic venous return from right to left across the VSD and into the aorta, producing arterial desaturation The amount of blood that shunts right to left through the VSD varies with the magnitude of the RV outflow tract obstruction and with SVR Distal PVR is low and has mini-mal influence on shunting Systemic vasodilation, in conjunction with increasing dynamic infundibular stenosis, intensifies

right-to-left shunting and can lead to hypercyanotic spells Such spells

can occur at any time before surgical correction of the anomalies and can be life-threatening Because the morbidity associated with recurrent hypercyanotic spells is significant, many physicians con-sider recurrent episodes of hypercyanosis an indication for correc-tive surgery at any age

Critical care management of TOF patients with hypercyanotic episodes should focus on minimizing oxygen consumption, aci-dosis, tachycardia, and acute elevations in PVR while augmenting preload and SVR Hypercyanotic spells in nonanesthetized chil-dren should initially be managed with 100% oxygen by facemask,

a knee-chest position or squat position (to increase SVR), and sedation Classically, intravenous morphine is used However, in-tranasal medications, such as fentanyl, have been used effectively when IV access has not yet been established Dexmedetomidine has been reported in the management of hypercyanotic spells, as

it provides not only sedation but also the additional benefit of lowering the heart rate.188 Regardless of the specific drug used, this regimen can usually stabilize the dynamic infundibular steno-sis while keeping SVR elevated Deeply cyanotic and lethargic patients are given rapid IV crystalloid infusions to augment circu-lating blood volume Continued severe hypoxemia should be treated with a vasopressor bolus (e.g., phenylephrine 1–2 mg/kg, titrated up to 5 mg/kg) to further augment SVR, and judicious use of IV propranolol or esmolol to slow the heart rate may be considered as necessary The latter allows more filling time and relaxes the infundibulum If a hypercyanotic spell persists despite treatment, either stabilization on VA ECMO or immediate surgi-cal intervention (palliative aortopulmonary shunt or complete repair) is indicated Induction of anesthesia must proceed cau-tiously after minimal fasting times and administration of a pre-medication, if possible The child can be anesthetized with IV narcotics and/or inhalational agents, but care must be taken to minimize reduction in SVR The pattern of mechanical ventila-tion is critical, as excessive intrathoracic pressure can further reduce antegrade flow across the RV outflow

Critical Care Management for the Early Postoperative Course

The surgical approach to the patient with TOF who presents with recurrent early hypercyanotic spells is variable Traditionally, com-plete repair is comcom-pleted at 3 to 6 months of age Delayed repair also is often necessary when a coronary artery crosses the RV out-flow tract, precluding transannular patch repair There are cur-rently two palliative interventions to facilitate a delayed repair

strategy The first is the use of a systemic-to-pulmonary artery

shunt Excellent outcomes have been achieved with this approach,

and the need for a transpulmonary valve annulus outflow patch at

the time of definitive surgery is reduced.189 However, the risks of

cyanosis and complications related to a systemic-to-pulmonary

artery shunt argue for early complete repair of TOF The

alterna-tive approach, developed more recently, is stenting the RV

out-flow tract in the cardiac catheterization laboratory.190 This

proce-dure has the additional benefit of improving pulmonary artery

growth prior to the definitive repair.191

Another approach for patients with TOF is to proceed with an

early complete repair For that method, a ventriculotomy is

per-formed in the RV outflow tract and frequently is extended distally

through the pulmonary valve annulus and beyond any associated

pulmonary artery stenosis The outflow tract is enlarged with

pericardium or synthetic material, and obstructing muscle

bun-dles are resected to relieve the outflow tract obstruction.192

Be-cause they are smaller and younger, these patients may be at

in-creased risk for complications associated with CPB Pulmonary

regurgitation results after a transannular incision that may

com-promise ventricular function in the postoperative period In

ap-proximately 8% of patients, abnormalities in the origin and

dis-tribution of the coronary arteries preclude placement of the RV

outflow patch, making it necessary to bypass the stenosis by

plac-ing an external conduit from the body of the right ventricle to the

pulmonary artery.193 , 194 An analysis of 3059 TOF repairs between

2002 and 2007 demonstrated that 83% (2534) had a complete

repair as their initial index procedure (with 6%, 19%, 38%, and

24% undergoing operation at the ages of 0 to 1, 1 to 3, 3 to 6,

and 6 to 12 months, respectively).195 There were 217 (7%)

pa-tients who underwent complete repair following initial palliation

Rates of ventriculotomy, transannular patch, and RV-PA conduit

use were significantly higher in those requiring initial palliation

Discharge mortality was higher in palliative patients versus initial

complete repair (7.5% vs 1.3%) There was less disparity in

dis-charge mortality between the two approaches among neonates

(6.2% vs 7.8%).195

When weaning patients from CPB following TOF repair, the

aim of therapy is to support RV function and minimize afterload

on the right ventricle This is particularly important following

repair in neonates or small infants Although systolic dysfunction

of the RV may occur following neonatal ventriculotomy, the

clinical picture is more commonly one of a restrictive physiology

reflecting reduced RV compliance or diastolic dysfunction.36 , 37

Factors contributing to diastolic dysfunction include

ventriculot-omy, lung and myocardial edema following CPB, inadequate

myocardial protection of the hypertrophied ventricle during

aor-tic cross-clamp, coronary artery injury, residual outflow tract

ob-struction, volume load on the ventricle from a residual VSD or

pulmonary regurgitation and arrhythmias

Patients usually separate from CPB with satisfactory blood

pressure and atrial filling pressures less than 10 mm Hg on modest

inotropic support However, in neonates during the first 6 to

12 hours after surgery, a low–cardiac output state with increased

right-sided filling pressures from diastolic dysfunction is common

following a right ventriculotomy Continued sedation and

paraly-sis usually are necessary for the first 24 to 48 hours to minimize

the stress response and associated myocardial work Preload must

be maintained despite elevation of RA pressure

In addition to high right-sided filling pressures, pleural

effusions or ascites may develop Inotropic support is often

re-quired and, if the blood pressure can tolerate it, introduction of a

phosphodiesterase inhibitor, such as milrinone, is beneficial be-cause of its lusitropic properties Bebe-cause of the restrictive physiol-ogy, even a relatively small volume load from a residual VSD or pulmonary regurgitation is often poorly tolerated in the early postoperative period; 2 to 3 days may be required before RV com-pliance improves and cardiac output increases Although the pat-ent foramen ovale or any ASD is usually closed in older patipat-ents

at the time of surgery, it is beneficial to leave a small atrial com-munication following neonatal repair In the face of diastolic dysfunction and increased RV end-diastolic pressure, a right-to-left atrial-level shunt maintains preload to the LV and, therefore, cardiac output Patients may be desaturated initially following surgery because of this shunting As RV compliance and function improve, the amount of shunt decreases and both antegrade pul-monary blood flow and systemic arterial oxygen saturation in-crease

Arrhythmias following repair include heart block, ventricular ectopy, and junctional ectopic tachycardia (JET) Maintaining sinus rhythm is important to optimize end-diastolic filling and minimize end-diastolic pressure AV pacing may be necessary for heart block Complete right bundle branch block is typical on the postoperative ECG Although JET is typically transient, it can result in significant deleterious effects on the child’s hemodynam-ics Treatment of JET may include sedation, cooling, paralysis, antiarrhythmic medications, temporary pacing, and, in rare cir-cumstances, mechanical support to maintain hemodynamics Most patients recover systolic ventricular function postopera-tively However, in a small group of patients, especially those paired at older ages, significant ventricular dysfunction re-mains.196 , 197 These patients can have left ventricular subendocardial ischemia that impairs LV myocardial mechanics.198 Pulmonary valve insufficiency may contribute to residual ventricular systolic dysfunction.199 The most common cause of systolic dysfunction immediately after repair of TOF is a residual or previously unrec-ognized VSD, which causes a volume load on the LV and pressure load on an already stressed RV, leading to RV failure and poor cardiac output.25 A residual VSD combined with residual RV outflow obstruction is particularly deleterious

In some patients, the distal pulmonary arteries may be so hypo-plastic and stenotic that they cannot be satisfactorily corrected Su-prasystemic pressure develops in the RV, which can be ameliorated

in some cases by partially opening the VSD to allow an intracardiac right-to-left ventricular shunt This shunt unloads the compromised

RV at the expense of decreased arterial oxygen saturation

Critical Care Management for Late Postoperative Care

Reconstruction of the RV outflow tract may lead to significant problems that affect RV function and risk for arrhythmias over time Although most of the long-term outcome data pertain to patients following TOF repair, similar complications and risks are likely for those who have undergone an extensive RV outflow re-construction, such as placement of a conduit from the RV to the pulmonary artery for correction of pulmonary atresia, truncus arteriosus, and the Rastelli procedure for transposition of the great arteries with pulmonary stenosis

Complete surgical repair of TOF has been successfully per-formed for more than 40 years, with studies reporting a 30- to 35-year actuarial survival of approximately 85%.200 Many pa-tients report leading relatively normal lives, but RV dysfunction may progress after repair and may be evident only on exercise stress testing or echocardiography A spectrum of problems may develop, ranging from a dilated RV with systolic dysfunction to

diastolic dysfunction from a poorly compliant RV Continued

evaluation is necessary because of the increased risk for ventricular

arrhythmias and late sudden death Factors that may adversely

affect long-term survival include older age at initial repair, initial

palliative procedures, and residual chronic pressure or volume

load as occurs from pulmonary insufficiency or stenosis

Systolic dysfunction secondary to a residual volume load from

pulmonary regurgitation after tetralogy repair is a predictor of late

morbidity It is reflected as cardiomegaly on chest radiograph, an

increase in RV end-diastolic volume and regurgitant volume by

echocardiography and cardiac MRI,12 and a reduction in

anaero-bic threshold, maximal exercise performance, and endurance on

exercise testing.201 Patients who have significant pulmonary

regur-gitation, RV dilation, and reduced RV function are at potential

risk for a fall in cardiac output during anesthesia, particularly as

positive-pressure ventilation may increase the amount of

regurgi-tation These patients currently benefit from early surgical

pulmo-nary valve replacement to reduce these symptoms and risks

An important group to distinguish consists of those who have

continued restrictive physiology or diastolic dysfunction

second-ary to reduced ventricular compliance They usually do not have

cardiomegaly, they demonstrate better exercise tolerance, and the

risk for ventricular dysrhythmias is possibly decreased Although

the RV is hypertrophied, function is generally well preserved on

echocardiography, with minimal pulmonary regurgitation The

incidence of significant RV outflow obstruction developing over

time is low Residual obstruction contributes to early mortality

within the first year after surgery but is well tolerated in the

long term

A wide variation in the incidence of ventricular ectopy has

been reported in numerous follow-up studies, including up to

15% of patients on routine ECG and up to 75% of patients on

Holter monitor Multiple risk factors—including older age at

re-pair, the extent of ventriculotomy, residual hemodynamic

abnor-malities, and duration of follow-up—have all been considered

important In common with these factors are probable myocardial

injury and fibrosis from chronic pressure and volume overload,

combined with cyanosis Although ventricular ectopy is common

in asymptomatic patients during ambulatory ECG, Holter

moni-toring, and exercise stress testing, it often is low grade and does

not identify those patients at risk for sudden death

Electrophysi-ologic induction of sustained ventricular tachycardia (VT),

especially when monomorphic, is suggestive of the presence of a

reentrant arrhythmic pathway Although dependent on the

stimu-lation protocol used to induce VT, the presence of monomorphic

VT in a symptomatic patient with syncope and palpitations is

significant and indicates treatment with radiofrequency ablation,

surgical cryoablation, antiarrhythmic drugs, or placement of an

implantable cardioverter-defibrillator.202 The risk for ventricular

dysrhythmias during anesthesia and ICU care for subsequent

hospitalizations is unknown Although preoperative prophylaxis

with antiarrhythmic drugs is not recommended, a means for

ex-ternal defibrillation and pacing must be readily available

Pulmonary Atresia

Pathophysiology

Atresia of the pulmonary valve or main pulmonary artery forms a

spectrum of cardiac defects Management depends on the extent

of atresia, size of the RV and TV, presence of a VSD and collateral

vessels, surface area of the pulmonary vascular bed, and coronary

artery anatomy The timing of developmental abnormality defines

the associated lesions Pulmonary atresia with intact ventricular septum (PAIVS) is primarily an abnormality of TV development that subsequently affects the pulmonary valve through its effects

on fetal RV growth Because the impact on the pulmonary valve

is late, the fetal truncus arteriosus has already divided and the mesenchymal distal pulmonary vasculature can connect to a main pulmonary artery pressure head appropriately As a result, this lesion predictably has well-developed central pulmonary arteries and pulmonary artery arborization

At one end of the spectrum of PAIVS, platelike pulmonary atresia overlaps with critical pulmonary stenosis where there is a mild or negligible degree of hypoplasia of the RV and TV In these lesions, a fixed obligatory right-to-left atrial-level shunt of all sys-temic venous return exists Some blood may flow into the RV, but because there is no outlet, blood regurgitates back across the TV and eventually reaches the LA and LV Pulmonary blood flow is derived exclusively or predominantly from a PDA As a rule, these patients do not have extensive aortopulmonary collateral blood flow; consequently, they often become cyanotic when the PDA closes after birth Critical pulmonary valve stenosis can be effec-tively treated by balloon valvuloplasty in the catheterization labo-ratory Antegrade flow across the RV outflow may not improve immediately but may gradually increase over days as RV compli-ance improves In platelike pulmonary atresia, radiofrequency perforation precedes balloon valvuloplasty

Most patients with PAIVS have an underdeveloped TV and

RV Depending on the degree of RV hypoplasia (which is directly related to the TV annulus z-score), the patient may be unsuitable for a biventricular repair in the long term In this situation, initial palliation with an aortopulmonary shunt is necessary However, if the RV is deemed to be of suitable size, then reconstruction of RV outflow with a pericardial patch or interventional catheter tech-niques may be considered (similar to the approach described ear-lier for platelike PA with mild RV hypoplasia) A large conal branch or aberrant left coronary artery across the RV outflow tract may restrict the size of a ventriculotomy and placement of a patch

or conduit

At the other end of the spectrum, severe pulmonary atresia may be associated with an extremely hypoplastic RV that is not suitable for biventricular repair A palliative procedure with a modified BT or central shunt usually is necessary at first to im-prove pulmonary blood flow, followed by staged single-ventricle repair (see the Fontan Procedure section)

Patients with PAIVS and severe RV hypoplasia may have nu-merous fistulous connections (sinusoids) between the small hy-pertensive RV cavity and coronary circulation.203 This is distinct from RV-dependent coronary circulation (RVDCC), in which these sinusoidal connections are accompanied by proximal steno-ses in the true coronary arteries If RV decompression or even staged palliation is being considered in such a patient, then a coronary angiogram is highly desirable to exclude this phenome-non In PAIVS with documented RVDCC, cardiac transplanta-tion is often the treatment of choice

In contrast to PAIVS, PA/VSD and TOF with PA represent an early failure of proper conotruncal development As a result, the mesenchymal segmental pulmonary arteries do not see the main pulmonary artery pressure head and instead form connections with the nearest alternative (aorta) This is the nature of the devel-opment of the aortopulmonary collaterals (APCs) associated with the lesion If the collaterals are substantial, defining a large pul-monary arterial segment, they are referred to as major aortopul-monary collateral arteries (MAPCAs) As a rule, these patients