Ebook Atrial fibrillation - A multidisciplinary approach to improving patient outcomes: Part 2

(BQ) Part 2 book Atrial fibrillation - A multidisciplinary approach to improving patient outcomes presents the following contents: LAA excision, ligation and occlusion devices; atrial fibrillation - a surgical approach; anesthesia care for the atrial fibrillation patient; team approach to the care of the AF patient; shared decision making for patients with atrial fibrillation, patient preferences and ecisionaids,...

Atrial fibrillation (AF) currently affects up to 5 million Americans and remains

the most common arrhythmia encountered in clinical practice.1,2 With an aging

population, the burden of AF is expected to rise 3-fold by 2050.3

Among the several downstream consequences of AF, the most feared is stroke

due to thromboembolism The primary cause of thrombus formation is

mechani-cal dysfunction in the atria, leading to impaired blood flow and stasis AF also

promotes endothelial dysfunction, inflammation, platelet activation, and

hyper-coagulability, which further contribute to thrombus formation.4–6

Stroke remains the number one cause of major disability and the third leading

cause of death in the United States.7 AF increases stroke risk 5-fold, leading to a

5% annual stroke rate for all-comers.7 Seen another way, the percentage of strokes

attributable to AF ranges from 1.5% in those aged 50 to 59 years to an

impres-sive 23.5% in those aged 80 to 89 years.7 While these statistics are dramatic, the

influence of AF on stroke is almost certainly underestimated as AF is commonly

silent and underdiagnosed.8

LEFT ATRIAL APPENDAGE

Johnson and colleagues described the left atrial appendage (LAA) as “our most

lethal human attachment.”9 Derived from the embryonic left atrium, the LAA

forms a blind pouch 2 to 4 cm long and most commonly lies on the anterior

sur-face of the heart Its narrow neck forms a natural obstacle to normal blood flow

The LAA endocardial surface is highly irregular due to the presence of pectinate

muscles This is in sharp contrast to the true left atrium, which is derived from

venous tissue and has a smooth endocardial surface The LAA also has a variable

number of lobes; an autopsy survey of 500 patients found that 20% had one lobe

while 77% had two or three lobes.10

Left Atrial Appendage Excision, Ligation, and Occlusion Devices

Taral K Patel, MD, and Bradley P Knight, MD

Atrial Fibrillation: A Multidisciplinary Approach to Improving Patient Outcomes © 2015

Joseph S Alpert, Lynne T Braun, Barbara J Fletcher, Gerald Fletcher, Editors-in-Chief,

Cardiotext Publishing, ISBN: 978-1-935395-95-9

and low blood flow during AF, is particularly susceptible to thrombus formation Studies using magnetic resonance imaging (MRI) and transesophageal echocar-diography (TEE) have suggested that larger LAA ostia, more lobes, and greater length all predict higher risk of stroke.11 An important review of 23 studies found that 17% of patients with nonrheumatic AF had left atrial thrombi, of which

a striking 91% were located in the LAA.12 It is now well-accepted that the vast majority of strokes caused by AF represent thromboembolism originating from the LAA

LIMITATIONS OF ORAL ANTICOAGULATION

Stroke prevention is the foundation of AF management Currently, the standard of care is oral systemic anticoagulation by using the widely adopted CHADS2 stroke risk-assessment tool.13,14 The newer CHA2DS2-VASc score has helped further refine stroke risk in patients with otherwise low CHADS2 scores.15 These scoring systems balance the bleeding risk from anticoagulation with the thromboembolic risk from untreated AF Supported by decades of data, oral anticoagulation has been unequivocally effective in reducing stroke Warfarin, still the predominant anticoagulant, was demonstrated to reduce AF-related stroke by 64% in an exten-sive meta-analysis.16

However, the widespread use of systemic anticoagulation has highlighted several important limitations of this strategy Most importantly, systemic anti-coagulation unavoidably increases bleeding risk Up to 40% of AF patients have relative or absolute contraindications to anticoagulation, usually owing to a his-tory of pathologic bleeding or an elevated risk of falls.17,18 The HAS-BLED score has helped quantify the bleeding risk of warfarin in a manner analogous to the CHADS2 score for stroke risk It is notable that several components of the HAS-BLED score—hypertension, prior stroke, and advanced age—are also found in the CHADS2 score In other words, patients at high risk for stroke also happen to be patients at high risk for bleeding, illustrating the complexity in properly selecting patients for oral anticoagulation

Aside from bleeding risk, warfarin use is further limited by the inconvenience

of frequent blood testing and extensive interactions with food and other tions Often because of these limitations, warfarin is not utilized in up to 50% of eligible AF patients.19 Even when patients are treated with warfarin, they spend

medica-up to half of the treatment time outside the therapeutic range.20

Motivated by the challenges of using warfarin, the newer oral anticoagulants dabigatran (a direct thrombin inhibitor), rivaroxaban (a factor Xa inhibitor), and apixaban (a factor Xa inhibitor) were developed and are now in general clinical

use These novel agents are comparably effective to warfarin with equivalent or

lower bleeding risk.21–23 They have the advantage of minimal food and drug

inter-actions and also eliminate the need for INR monitoring, increasing the ease of

use and compliance Unfortunately, they still suffer from the problem of elevated

bleeding risk; this risk is further heightened because, unlike warfarin, the new

drugs are not easily reversible with blood-product transfusion Finally, the new

agents are more costly and, at present, it is unclear whether they are truly cost

effective in comparison with warfarin

Even with improved oral anticoagulation options, there remains a more

fun-damental issue Because AF-related stroke appears to be largely a focal problem—

thromboembolism from the LAA—a focal approach would be preferable to the

currently imprecise strategy of systemic anticoagulation Theoretically, a

proce-dure to exclude the LAA (either by excision or by ligation or occlusion) should

offer similar stroke prophylaxis while eliminating the disadvantages of systemic

anticoagulation LAA exclusion would be especially appealing for patients with

either intolerance or contraindications to anticoagulation In recent years,

sub-stantial progress has been made in developing techniques to exclude the LAA as

a viable alternative for stroke prevention in AF

LEFT ATRIAL APPENDAGE EXCLUSION: 

SURGICAL TECHNIQUES

LAA exclusion was first reported in 1949, when the surgeon Madden24 published

a case series of 2 patients who underwent LAA removal as a prophylaxis for

recur-rent arterial emboli The high morbidity and mortality of the procedure prevented

its widespread adoption for decades, until interest was reignited in the 1990s by

the development of the Cox-Maze III procedure, which included removal of the

LAA.25 Surgical techniques have evolved along two lines: LAA exclusion (using

various suture techniques) and LAA excision (via surgical stapler or removal with

oversew)

Data for LAA surgery consist primarily of case reports and retrospective case

series Intepretation of the data is hampered by nonuniform surgical techniques

and nonstandardized outcomes measurements The use of TEE, considered the

gold standard for LAA visualization, is absent in many reports A large review

of existing literature found that surgical success was highly dependent on both

operator and technique; complete LAA closure rates ranged from 17% to 93%.26

Excision and oversew appeared to demonstrate the most durable results A recent

pilot trial randomized 51 patients to surgical LAA closure versus oral

anticoagu-lation and demonstrated comparable stroke rates during follow-up.27 The results

LAA exclusion effectively reduces stroke risk.

Current ACC/AHA guidelines limit surgical LAA exclusion as an adjunctive procedure during mitral valve or Maze surgery.13 However, two recently developed devices may rekindle interest in stand-alone surgical LAA exclusion The first, AtriClip LAA Exclusion System (Atricure, West Chester, OH), is approved in both the United States and Europe, although it is indicated only in conjunction with other open cardiac surgical procedures in the United States The device consists of a tita-nium ring covered by a woven polyester fabric Under direct visualization, the clip

is secured around the base of the LAA using a special deployment tool In the est trial to date, 70 patients undergoing open cardiac surgery in seven US centers had the AtriClip successfully placed.29 Of the 61 patients who underwent imaging

larg-at 3 months, 60 achieved persistent LAA exclusion There were no device-specific adverse events reported Although this was a small study with short-term follow-up,

it demonstrated that the device could be deployed safely during open cardiac surgery.The second device involves a minimally invasive thoracoscopic approach After left lung deflation, an endoscopic cutter (Ethicon Endo-Surgery, Cincinnati, OH)

is introduced via the left lateral thorax The cutter then simultaneously removes the LAA and staples its base closed The procedure eliminates the need for tho-racotomy, although concerns remain about the risks of lung deflation and the potential for catastrophic bleeding into a closed chest Ohtsuka et al.30 published their experience with the technique in 30 patients with prior thromboembolism, achieving 100% procedural success and no major complications Anticoagulation was discontinued and no recurrence of thromboembolism occurred after 18 months of follow-up These preliminary data suggest that stand-alone surgical LAA exclusion may eventually have a place alongside the various transcatheter techniques

LEFT ATRIAL APPENDAGE EXCLUSION: 

TRANSCATHETER TECHNIQUES

In an effort to avoid the morbidity of open surgery for LAA exclusion, minimally invasive percutaneous techniques have rapidly developed over the past decade Of these, 4 have been tested in humans and shown promise

PLAATO Device

Important for historical purposes, the Percutaneous LAA Transcatheter Occlusion (PLAATO) device (ev3 Endovascular, Plymouth, MN) became the first device of

its kind deployed in humans in 2001 The device consisted of a self-expanding

nitinol cage covered by a blood-impermeable polytetrafluoroethylene membrane

(Figure 8.1) The device was deployed in the LAA via transseptal catheterization

under fluoroscopic and TEE guidance Clinical experience with PLAATO was

reported in 3 small studies Sievert et al.31 implanted the device in 15 patients

with 100% procedural success and one incident of hemopericardium A larger

international registry of 111 patients reported a 97% implant success rate and a 6%

adverse event rate, including one death.32 The 10-month stroke rate of 2.2%

com-pared favorably with the CHADS2-predicted rate of 6.3% A North American

reg-istry of 64 patients reported 100% procedural success.33 After 5 years of follow-up,

the stroke rate was 3.8%, a relative risk reduction of 42% from the expected stroke

rate of 6.6% Despite this promising clinical experience, the PLAATO device was

withdrawn from development in 2006 However, its design became the inspiration

for the subsequently developed WATCHMAN device

WATCHMAN Device

The WATCHMAN device (Boston Scientific, Natick, MA) was first implanted

in 2002 It also consists of a self-expanding nitinol frame, but is open-ended and

has a permeable polyethylene membrane that only covers the part of the device

exposed to the left atrium (Figure 8.2) The WATCHMAN device is also delivered

via a transseptal system (Figure 8.3) Initial protocols required at least 6 weeks

Fig u r e 8 1

The PLAATO device, mounted on its delivery catheter Source: Reprinted with permission from Syed T, Halperin J Nat Rev Cardiol 2007:4;428–435

Fig u r e 8 2

(A) The WATCHMANdevice consists of a nitinol frame and permeable membrane

(B) Illustration of the device properly deployed in the left atrial appendage Source: Used with permission of Boston Scientific Corporation

of warfarin post-implant to prevent thrombus formation prior to device

endo-thelialization Warfarin was discontinued once a follow-up TEE demonstrated

no flow into the LAA, signifying complete endothelialization Subsequently, a

strategy of substituting dual antiplatelet therapy for warfarin was evaluated in

150 warfarin-ineligible patients who underwent WATCHMAN implantation.34

After 14 months of follow-up, the actual ischemic stroke rate was 1.7% compared

with the CHADS2-predicted rate of 7.3%, demonstrating that WATCHMAN

implantation without a warfarin transition was a viable alternative for patients

with contraindications to anticoagulation

Following several feasibility studies, the WATCHMAN device underwent

a head-to-head trial against warfarin in the landmark PROTECT-AF trial.35

Fig u r e 8 3

Fluoroscopic image of the WATCHMAN device (arrow) deployed in the left atrial appendage

sion with anticoagulation In PROTECT-AF, 707 patients from 59 centers in the United States and Europe were randomized 2:1 to WATCHMAN versus warfarin therapy Patients had relatively low stroke risk (68% had a CHADS2 score of 1 or 2) and no contraindications to warfarin Overall implant success rate was 91% and

at 6 months, 92% of patients in the WATCHMAN arm had discontinued agulation The trial was designed to test noninferiority of WATCHMAN to stan-dard warfarin therapy After 1065 patient-years, the primary efficacy end point (stroke, systemic embolism, or cardiovascular or unexplained death) was superior

antico-in the WATCHMAN arm versus the warfarantico-in arm (3.0% vs 4.9% per 100 years), fulfilling the criteria for noninferiority However, the primary safety end point (excessive bleeding or procedure-related complications) was worse in the WATCHMAN group (7.4% vs 4.4%) Procedure-related complications included

patient-22 pericardial effusions, 4 air emboli, and 3 device embolizations On the other hand, the warfarin group had higher rates of major bleeding (4.1% vs 3.5%) and hemorrhagic stroke (2.5% vs 0.2%)

In 2013, the 2.3-year results of PROTECT-AF were published, highlighting the durability of the initial results.36 After 1588 patient-years, the primary effi-cacy end point occurred in 3.0% of WATCHMAN patients and 4.3% of warfarin patients, again meeting criteria for noninferiority With respect to the safety event rate, the WATCHMAN group continued to fare worse (5.5% vs 3.6%), although the gap had narrowed As expected, the adverse events in the WATCHMAN group were driven by early procedure-related complications, with relatively few events occurring in follow-up On the other hand, adverse events continued to gradually acrue in the warfarin arm, driven primarily by warfarin-related bleeding Despite the generally positive reception for PROTECT-AF, concerns still remain regard-ing periprocedural complications and thrombus formation on the device prior to endothelialization (Figure 8.4)

Of note, procedure-related complications were greater in the first half of PROTECT-AF than in the second half, underscoring the learning curve involved with device implantation; adverse events continued to remain low in the Continued Access Protocol (CAP) registry of 460 patients.37 A second random-ized trial of WATCHMAN versus warfarin, called PREVAIL, sought to address concerns about the high adverse-event rate from WATCHMAN implantation The preliminary data appear promising and are currently under peer review Another registry (Continued Access to PREVAIL) has also been created to generate more safety and efficacy data In late 2013, the accumulated WATCHMAN data was compelling enough for an FDA advisory panel to vote strongly in favor of the device when asked if its benefits outweigh its risks, likely paving the way for even-tual FDA approval

At present, the WATCHMAN device is the only LAA exclusion device

with demonstrated noninferiority to warfarin for stroke prevention There is

also evidence that patients achieve improvement in quality-of-life measures

after WATCHMAN implantation, likely due to discontinuation of daily

warfa-rin, reduction in bleeding complications, and elimination of dietary and drug

interactions.38

Fig u r e 8 4

Transesophageal echocardiographic image of a thrombus (arrow) on a WATCHMAN device several months after anticoagulation was discontinued

AMPLATZER Cardiac Plug

After the success of the AMPLATZER Septal Occluder (St Jude Medical, Plymouth, MN) for patent foramen ovale and atrial septal defect closure, the prod-uct was redesigned specifically for the LAA and named the AMPLATZER Cardiac Plug (ACP; St Jude Medical) (Figure 8.5) This device consists of a self-expanding nitinol mesh constructed in two parts: a distal lobe designed to prevent device migration and a proximal disk designed to occlude the LAA ostium The lobe and disk are joined by an articulating waist that accommodates anatomic variation The ACP is also delivered transseptally to the LAA

Three published registries summarize the worldwide data on the ACP The initial human experience in Europe demonstrated a 96% implant success rate

in 137 patients, with serious complications in 10 patients (including 3 ischemic strokes, 5 pericardial effusions, and 2 device embolizations).39 The Asian-Pacific experience, although consisting of only 20 patients, provided one-year follow-up data demonstrating no incidence of stroke or death.40 Finally, a Canadian registry

of 52 patients achieved procedural success in all but one patient.41 Of note, the Canadian patients all had contraindications to anticoagulation Two serious com-plications occurred (one device embolization and one cardiac tamponade) TEE at

6 months showed a disappointing 16% rate of peri-device leak, but 20-month low-up demonstrated no incidence of device-related death or thromboembolism Importantly, ACP implantation protocols have generally not involved peri-procedural anticoagulation, instead employing dual antiplatelet therapy for one month followed by aspirin monothereapy Concerns remain about the incidence

fol-of persistent leaks following device implantation While achieving CE mark approval in Europe, the ACP is still in Phase I clinical trials in the United States

LARIAT Suture Delivery System

Receiving FDA approval in 2009 for soft tissue approximation, the LARIAT suture delivery system (SentreHEART, Palo Alto, CA) is the newest LAA exclu-sion device This hybrid system involves both epicardial and transseptal access Epicardial and endocardial magnet-tipped guidewires meet at the tip of the LAA, forming a single rail for the delivery of an epicardial snare with a pre-tied suture loop A balloon catheter serves as a marker for the LAA base and stabilizes the epicardial snare (Figure 8.6) Under fluoroscopic and TEE guidance, the suture is tightened around the LAA base and released from the snare Importantly, LAA closure can be evaluated in real-time with TEE or left atrial angiography If clo-sure is not satisfactory, the snare can be repositioned prior to irreversible suture release (Figure 8.7)

Fig u r e 8 5

The AMPLATZER Cardiac Plug (A) mounted on its delivery catheter and (B) properly deployed in the left atrial appendage Source: Reproduced with permission from Jain A, Gallagher S Heart 2011:97;762–765

Fluoroscopic sequence of the LARIAT procedure (A) After transseptal and pericardial

access, baseline left atrial angiography identifies the left atrial appendage (B)

Magnet-tipped endocardial and epicardial guidewires make contact across the wall of the left atrial appendage (C) The balloon catheter is inflated just within the ostium of the left atrial

appendage, guiding the placement of the epicardial snare (D) The snare is tightened at

the base of the left atrial appendage (E) The balloon catheter is pulled back, and left atrial angiography confirms occlusion of the left atrial appendage (F) The suture is cinched down permanently, the snare is retracted, and a final left atrial angiogram reconfirms complete

occlusion of the left atrial appendage

This hybrid approach offers several theoretical advantages, including

com-plete control of the pericardial space in the event of cardiac perforation, lack of

any endovascular hardware left behind, and possible elimination of the need for

postprocedure anticoagulation The major disadvantage of the LARIAT system is

the need for both transseptal and pericardial access Additionally, anatomic

vari-ables can limit candidacy, such as LAA diameter greater than 40 mm, posteriorly

rotated LAA, or pericardial adhesions from prior pericarditis or cardiac surgery

The first human experience with the LARIAT system consisted of 10 patients,

all of whom attained complete LAA exclusion.42 A large-scale, single-center

experi-ence was then published in 2013.43 Of note, patients in this registry were relatively

low risk; 73% had a CHADS2 score of 1 or 2, and only 6% had contraindications

to anticoagulation Eighty-five of 89 patients underwent successful LAA ligation

Eighty-one patients had complete closure immediately, and 4 patients had a 2- to

3-mm residual leak The 3 acute complications were all access-related (2 pericardial

and one transseptal) At one-year follow-up, there were 2 incidents of severe

peri-carditis, one late pericardial effusion, 2 unexplained deaths, and 2 strokes thought

to be nonembolic One-year TEE showed a 98% rate of complete LAA closure

A multicenter US registry recently presented its initial results in abstract form

(Transcatheter Cardiovascular Therapeutics 2013 Meeting) The registry included

151 patients with a median CHADS2 score of 3 Although technical success was

achieved in 94% of cases, significant pericardial effusions occurred in 16 patients,

major bleeding in 14 patients, and emergency surgery in 3 patients Late

pericar-dial effusions (after hospital discharge) occurred in 3 patients Follow-up TEE was

performed in only 40 patients, but 6 demonstrated residual LAA communication,

and 4 showed thrombus at the suture site

These findings raise concerns about the durability of the LARIAT method, the

intense pericardial inflammation caused by the strangulated LAA, and the local

inflammation and thrombogenicity at the endocardial site of LAA closure.44 The

LARIAT protocol will likely need to account for these safety concerns, for instance

by incorporating anticoagulation and anti-inflammatory medications for several

weeks to months postprocedure At present, further safety and efficacy data are

being generated for the LARIAT system

CONCLUSIONS

Stroke prevention in AF presents significant challenges as well as opportunities

The current standard of care, systemic anticoagulation, is effective but suffers

from several limitations including bleeding risk, poor compliance, intolerance,

inconvenience, and a lifelong commitment to daily medication These concerns

open the door for a new strategy for stroke prevention, one targeted to the ultimate

rally appealing, as it represents a focused intervention for a largely focal problem.

A variety of techniques for LAA exclusion are now in development Although open-chest surgical exclusion will continue to have a limited role as a concomitant procedure during cardiac surgery, efforts are more focused on minimally invasive closed chest and transcatheter techniques With lower morbidity and mortality, modern LAA exclusion is no longer an unpalatable idea and represents a viable option in specific AF patients

Several questions remain regarding LAA exclusion With only one randomized clinical trial to date, the data are still in their infancy Information regarding long-term durability of LAA exclusion is not yet available Even after acute procedural success, there often remains a small diverticulum or stump at the LAA ostium Given the surgical data that incomplete closure is worse than no closure at all, there are valid concerns about the thrombogenicity of this unnatural diverticulum.26

The data also reinforce the presence of a learning curve, showing that cess rates are highly operator- and experience-dependent As the field evolves to second- and third-generation data, the hope is that success rates will improve and complication rates will drop Data from the WATCHMAN experience already support this notion

suc-The dominance of one percutaneous technique over the rest is unlikely More likely, choice of technique will depend on patient characteristics For example, prior cardiac surgery would limit pericaridal access, making the WATCHMAN

or ACP preferable On the other hand, recurrent endocarditis would make the LARIAT or thoracoscopic systems more attractive, given their lack of endovas-cular hardware Additionally, long-term safety and efficacy data will ultimately determine which techniques will survive

Another issue is the appropriate selection of candidates for LAA exclusion Given the infancy of the field, current focus has naturally been on patients who are poor candidates for standard anticoagulation As protocols evolve regarding the need for post-implant anticoagulation, patient selection will necessarily evolve

as well But whether LAA exclusion will be offered as an equal or preferred native to anticoagulation remains to be seen Only the WATCHMAN device has high-level data compared with anticoagulation (and only to warfarin) Although noninferiority has been demonstrated, a trial demonstrating long-term superi-ority of LAA exclusion is lacking Also noteworthy, all protocols have excluded patients with valvular AF or prosthetic heart valves; the role of LAA exclusion in these patients is unknown Finally, data comparing LAA exclusion to the novel anticoagulants are glaringly absent It is generally believed that the newer agents will be shown to have a superior risk/benefit ratio to warfarin LAA exclusion may not provide a clear benefit compared with these agents

alter-The goal of LAA exclusion is to replace the lifelong need for anticoagulation

with a single procedure with small upfront risks and durable long-term benefits

This goal assumes that stroke risk in AF is entirely explained by the LAA While it

is clear that the LAA harbors the majority of the risk, data also suggest that AF is

associated with a systemic hypercoagulable state, which contributes to stroke risk

in an independent and meaningful way.45 This argues against an all-or-none

strat-egy for LAA exclusion and suggests a continued role for anticoagulation despite

successful LAA exclusion Future work will help shed light on this important

question

Despite the challenges, the field of LAA exclusion has grown dramatically and

represents a promising alternative to anticoagulation for preventing AF-related

stroke Currently, LAA exclusion is best suited for patients with intolerance or

contraindications to oral anticoagulation, which remains the standard of care It

is too early to consider LAA exclusion a paradigm shift in stroke prevention, but

further studies will help solidify its eventual role in AF management

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Watchman device in patients with a contraindication for oral anticoagulation: the ASAP

study (ASA Plavix Feasibility Study With Watchman Left Atrial Appendage Closure

Technology) J Am Coll Cardiol 2013;61(25):2551–2556.

35 Holmes DR, Reddy VY, Turi ZG, et al Percutaneous closure of the left atrial appendage

versus warfarin therapy for prevention of stroke in patients with atrial fibrillation: A

ran-domised non-inferiority trial Lancet 2009;374(9689):534–542.

36 Reddy VY, Doshi SK, Sievert H, et al Percutaneous left atrial appendage closure for stroke

prophylaxis in patients with atrial fibrillation: 2.3-Year Follow-up of the PROTECT AF

(Watchman Left Atrial Appendage System for Embolic Protection in Patients with Atrial

Fibrillation) Trial Circulation 2013;127(6):720–729.

37 Reddy VY, Holmes D, Doshi SK, Neuzil P, Kar S Safety of percutaneous left atrial appendage

closure: results from the Watchman Left Atrial Appendage System for Embolic Protection

in Patients with AF (PROTECT AF) clinical trial and the Continued Access Registry

Circulation 2011;123(4):417–424.

38 Alli O, Doshi S, Kar S, et al Quality of life assessment in the randomized PROTECT

AF (Percutaneous Closure of the Left Atrial Appendage Versus Warfarin Therapy for

Prevention of Stroke in Patients With Atrial Fibrillation) trial of patients at risk for stroke

with nonvalvular atrial fibrillation J Am Coll Cardiol 2013;61(17):1790–1798.

39 Park JW, Bethencourt A, Sievert H, et al Left atrial appendage closure with Amplatzer

cardiac plug in atrial fibrillation: initial European experience Cathet Cardiovasc Interv

2011;77(5):700–706.

40 Lam YY, Yip GW, Yu CM, et al Left atrial appendage closure with AMPLATZER

car-diac plug for stroke prevention in atrial fibrillation: Initial Asia-Pacific experience Cathet

Cardiovasc Interv 2012;79(5):794–800.

41 Urena M, Rodes-Cabau J, Freixa X, et al Percutaneous left atrial appendage closure with

the AMPLATZER cardiac plug device in patients with nonvalvular atrial fibrillation and

contraindications to anticoagulation therapy J Am Coll Cardiol 2013;62(2):96–102.

42 Bartus K, Bednarek J, Myc J, et al Feasibility of closed-chest ligation of the left atrial

append-age in humans Heart Rhythm 2011;8(2):188–193.

43 Bartus K, Han FT, Bednarek J, et al Percutaneous left atrial appendage suture ligation using

the LARIAT device in patients with atrial fibrillation: Initial clinical experience J Am Coll

Cardiol 2013;62(2):108–118.

44 Giedrimas E, Lin AC, Knight BP Left atrial thrombus after appendage closure using

LARIAT Circ Arrhythm Electrophysiol 2013;6(4):e52–e53.

45 Watson T, Shantsila E, Lip GY Mechanisms of thrombogenesis in atrial fibrillation:

Virchow’s triad revisited Lancet 2009;373(9658):155–166.

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia, present

in approximately 2% of the general population and 10% of individuals over the

age of 80.1–5 The treatment of AF results in a significant financial burden, with

an estimated annual cost of $8705 per patient, and a total annual cost of over

$6 billion in the United States alone.6 AF is associated with significant morbidity

and mortality related to its three detrimental sequelae, which include: (1)

pal-pitations, which cause patient discomfort and anxiety; (2) loss of synchronous

atrioventricular (AV) contraction, compromising cardiac hemodynamics,

result-ing in ventricular dysfunction; and (3) stasis of blood flow in the left atrium (LA),

which can result in thromboembolism and stroke.7–11 An understanding of these

sequelae has been important in the development of surgical procedures to treat

medically refractory AF

HISTORY OF SURGICAL ABLATION FOR AF

Because of the poor efficacy of medical therapy for AF, several surgical procedures

were developed in the 1980s, which led to the introduction of the current

gold-standard surgical treatment for AF, the Cox-Maze (CM) procedure In 1980, Dr

James Cox developed the left atrial isolation procedure, which attempted to

con-fine AF to the LA.12 By taking advantage of the fact that the sinoatrial (SA) node,

AV node, and internodal pathways are located in the right atrium (RA) and

intra-atrial septum, the procedure allowed for restoration of normal sinus rhythm (SR)

after electrically isolating the LA from the rest of the heart This procedure was

beneficial in that it corrected 2 of the 3 sequelae of AF By resuming normal SR

between the RA and ventricle, right-sided synchrony was reestablished, resulting

in an improvement in right-sided cardiac output and improved hemodynamics

Atrial Fibrillation: A Surgical

Approach to Improving

Patient Outcomes

Christopher P Lawrance, MD, and Ralph J Damiano, Jr., MD

Atrial Fibrillation: A Multidisciplinary Approach to Improving Patient Outcomes © 2015

Joseph S Alpert, Lynne T Braun, Barbara J Fletcher, Gerald Fletcher, Editors-in-Chief,

Cardiotext Publishing, ISBN: 978-1-935395-95-9

not address the risk of thromboembolism The procedure also did not address patients in whom AF originated outside of the LA.

Scheinman et al.13 described catheter ablation of the His bundle, which was successful in electrically isolating the atria from the ventricles While allowing for rate control, this procedure necessitated the need for a permanent pacemaker

to restore normal ventricular rhythm The procedure also allowed both atria to remain in AF, thereby causing dyssynchrony between the contractions of the atria and ventricles, and did not address the risk of thromboembolism Despite these limitations, this procedure is still used in symptomatic patients who are refrac-tory to medical therapy and are poor candidates for curative but more invasive procedures

Sharma et al.14 introduced the corridor procedure for the treatment of AF This operation involved isolating a strip of atrial septum that contained both the

SA node and AV node from surrounding atrial tissue This allowed the SA node alone to drive ventricular contraction, correcting the irregular heart rhythm This procedure, however, allowed most of the atria to remain in AF and did not address either the AV dyssynchrony or the risk of thromboembolism

DEVELOPMENT OF THE COX-MAZE 

PROCEDURE

The first clinically successful surgical procedure for the treatment of AF was duced in 1987 by Dr James L Cox at Washington University in St Louis, MO after nearly a decade of basic research.15–17 This procedure, the Cox-Maze procedure, was designed to interrupt the macro-reentrant circuits that were thought to be respon-sible for AF, thereby making it impossible for the atrium to maintain AF or atrial flutter Compared with previous attempts at surgically correcting AF, the Cox-Maze procedure preserved SR and maintained AV synchrony, thus decreasing the risk of thromboembolism and stroke The operation involved creating multiple incisions across both the left and right atria in a way such that the SA node could still activate most of the atrial tissue and thus preserve atrial contraction Shortly after the clinical implementation of the Cox-Maze procedure, the procedure was modified because

intro-of late chronotropic incompetence in many patients which required pacemaker implantation The new modification was coined the Cox-Maze II Unfortunately, this lesion set proved to be technically difficult to perform, so it was again modified

to the Cox-Maze III (Figure 9.1) The Cox-Maze III was widely adopted in the 1990s and became the gold standard for the surgical treatment of AF owing to its ability to restore sinus rhythm in over 90% of patients with symptomatic AF.18

Although results using the Cox-Maze III were excellent, the operation was

limited in its use because of its technical difficulty Few surgeons were willing

to add the procedure to concomitant operations because of the associated long

cardiopulmonary bypass (CPB) times As a result, <1% of patients with AF

receiv-ing cardiac surgery also received a Cox-Maze III operation.19 Advances in

abla-tion technology have revoluabla-tionized the surgical treatment of AF over the last

15 years Experimental studies using bipolar radiofrequency (RF) clamps showed

that linear lines of ablation could effectively reproduce the traditional

“cut-and-sew” technique.20 This experimental work led to the clinical adoption of bipolar

RF ablation and cryoablation to replace most of the incisions of the Cox-Maze III

This new procedure has been termed the Cox-Maze IV (Figure 9.2).21 Clinical case

series have revealed that the Cox-Maze IV has equal efficacy and lower CPB times

than the Cox-Maze III.22 It was also realized that the use of ablation technology

allowed for the development of minimally invasive approaches

PATIENT SELECTION

The Heart Rhythm Society, in partnership with the European Heart Rhythm

Association, the European Cardiac Arrhythmia Society, the American College of

Cardiology, the American Heart Association, and the Society of Thoracic Surgeons

created a consensus statement in 2007 to evaluate the indications for both catheter

Fig u r e 9 1

Cut-and-sew Cox-Maze III lesion set Source: Adapted from Cox JL, Boineau JP, Schuessler RB,

et al J Thorac Cardiovasc Surg 1995;110:473–484

and surgical ablation of AF, which was later revised in 2012.23 The consensus of the task force was that the following were appropriate indications for the surgical ablation of AF: (1) symptomatic or selected asymptomatic AF patients undergoing cardiac surgery in whom the ablation can be performed with minimal risk, and (2) stand-alone AF surgery should be considered for symptomatic AF patients who have failed medical management and either prefer a surgical approach, have failed catheter ablation, or are not candidates for catheter ablation In our opinion, other patients who should be considered are patients with a CHADS2 score of ≥2 who have developed a contraindication to warfarin, or patients who have had a stroke while being properly anticoagulated In patients with a CHADS2 score ≥2 referred for a Cox-Maze procedure at our institution, the overall annual risk of a late neurologic event was decreased to 0.2% after the surgery with the majority of patients off all anticoagulation.24

SURGICAL TECHNIQUES 

Traditionally, the Cox-Maze IV procedure has been performed through a omy which is described below However, advances in minimally invasive surgery have allowed the procedure to be performed through a (5–6 cm) right minitho-racotomy (RMT) in most patients.25,26 Contraindications to this approach include patients with severe respiratory disease, previous right thoracotomy, or aortoiliac

sternot-Fig u r e 9 2

Bipolar radiofrequency ablation Cox-Maze IV schematic

disease The RMT is performed using single-lung inflation and femoral

cannula-tion for CPB The lesion set is largely the same between the two approaches with

the exceptions described below Regardless of the approach, all patients have

intra-operative transesophageal echocardiograms to evaluate for the presence of left

atrial thrombus Patients in AF at the time of surgery are electrically cardioverted

It should be noted that each RF ablation line is created by performing 2 to 3

abla-tions with the clamp to ensure transmural ablation

Preparation and Pulmonary Vein Isolation

The patient is prepped and draped in the supine position and a median

ster-notomy is performed A pericardial cradle is created and central cannulation is

performed While on normothermic CPB, both the right and left pulmonary veins

(PVs) are bluntly dissected at their confluences and surrounded with umbilical

tape when performed through a sternotomy The bipolar RF clamp is first passed

around the right and then the left PVs, incorporating as generous a cuff of atrial

tissue as possible Typically 2 to 3 ablations are performed around this cuff to

ensure a circumferential transmural ablation When performed through a RMT,

only the right PVs are epicardially isolated The left PVs are endocardially isolated

during the creation of the LA lesion set later in the procedure Exit block is

con-firmed by documenting failure to pace from each PV when performed through a

sternotomy and from the right PVs when performed through a RMT

Right Atrial Lesion Set

The RA lesion set can be seen in Figure 9.3 The patient is cooled to 34°C and

while the heart is beating, a pursestring is placed at the base of the RA

append-age (RAA) Through this pursestring, the jaw of the bipolar RF clamp is inserted

into the RA An ablation line is created along the RA free wall toward the

supe-rior vena cava (SVC) A vertical atriotomy is then performed extending from the

intra-atrial septum toward the AV groove, near the free margin of the heart This

incision should be at least 2 cm from the previous RA free wall ablation line to

avoid creating an area of slow conduction When performed through a RMT, this

incision is replaced by two additional pursestrings (Figure 9.3B) From the inferior

aspect of the atriotomy, bipolar RF ablation lines are created up to the SVC and

down to the inferior vena cava (IVC) From the superior aspect of the atriotomy,

a 3-cm linear cryoprobe is used to create an endocardial ablation down to the

2 o’clock position of the tricuspid valve Cryoablation is used to create lesions near

the annular tissue because of its ability to create transmural lesions while

main-taining the fibrous structure and integrity of the annulus and valvular tissue, as

opposed to RF ablation The cryoprobe is then placed through the previous RAA pursestring suture, and an endocardial cryoablation is performed down to the 10 o’clock position of the tricuspid valve.

Left Atrial Lesion Set

The LA lesion set is depicted in Figure 9.4 The aorta is cross-clamped and grade cold-blood cardioplegia is administered With the heart arrested, the left atrial appendage (LAA) is amputated Through this incision, one jaw of the bipo-lar RF clamp is inserted and an ablation line is created connecting to either the left superior or inferior PV The LAA is then oversewn in two layers Methylene blue is used to mark the coronary sinus between the left and right coronary arte-rial circulations A standard horizontal left atriotomy is performed and can be extended superiorly onto the dome of the LA or inferiorly around the right infe-rior PV as needed Two separate ablation lines are created from the super and inferior aspects of the atriotomy toward the left superior and inferior pulmonary vein orifices, respectively These two connecting lesions, in addition to the PV isolation, complete the “box lesion.” In the RMT approach, isolation of the left PVs

antero-is performed by sequential endocardial cryoablations behind the left PVs, necting the two previous LA roof and floor RF ablation lines (Figure 9.4B) A final bipolar RF ablation line is created from the inferior aspect of the left atriotomy, across the floor of the LA, toward the mitral valve annulus This ablation crosses

con-Fig u r e 9 3

Right atrial Cox-Maze IV lesion set A: Lesion set performed through a sternotomy incision

Source: Adapted from Damiano RJ, Jr., Schuessler RB, et al J Thorac Cardiovasc Surg

2011;141:113–121 B: Lesion set performed through a right mini-thoracotomy

Source: Adapted from Robertson JO, Damiano RJ, Jr, et al Ann of Cardiothorac Surg

2014;3:105–116

the coronary sinus at the position previously marked with methylene blue The

AV groove, which contains thicker tissue, lies in this area, so cryoablation is used

to bridge the 1- to 2-cm gap from the end of this RF ablation line to the mitral

valve annulus This lesion is called the LA isthmus ablation To complete the LA

lesion set, the coronary sinus is ablated epicardially with a cryoprobe in line with

the endocardial isthmus lesion

RECOVERY AND COMPLICATIONS

The postoperative management is similar for both the RMT and sternotomy

approaches The most common complication of the Cox-Maze IV procedure has

been postoperative arrhythmias, specifically junctional and atrial tachyarrhythmias

(ATAs) Postoperatively, the RA is paced at 80 to 100 beats per minute (bpm) AV

sequential pacing is used if the patient develops heart block Diagnoses of

arrhyth-mias is aided by performing an ECG using the atrial lead to establish the presence of

P waves, because these can be difficult to visualize on a routine ECG after a Cox-Maze

procedure Most patients are in junctional rhythm right after the procedure, and this

usually resolves within the first few days Antiarrhythmic drugs should not be started

in patients with a junctional rhythm until they recover their sinus rhythm

Over 40% of patients will develop ATAs postoperatively, and these usually

subside after the first month Hemodynamically stable ATAs should be rate

Fig u r e 9 4

Left atrial Cox-Maze IV lesion set A: Lesion set performed through a sternotomy incision

Source: Adapted from Damiano RJ, Jr., Schuessler RB, et al J Thorac Cardiovasc Surg

2011;141:113–121 B: Lesion set performed through a right mini-thoracotomy Source: Adapted from Robertson JO, Damiano RJ, Jr, et al Ann Cardiothorac Surg 2014;3:105–116

ATAs are usually DC cardioverted at 3 to 4 weeks, after the surgical inflammation subsides, reducing the risk of recurrence Finally, warfarin should be started on all patients and continued for at least 3 months postoperatively unless otherwise contraindicated

If patients are in sinus rhythm at 2 months, antiarrhythmic medications are discontinued At 3 to 4 months with patients off all antiarrhythmic medications, a 24- to 48-hour prolonged Holter monitor is obtained to demonstrate the absence

of ATAs A transthoracic echocardiogram is also obtained, in patients in sinus rhythm and with no evidence of atrial stasis on echocardiography, it is our policy

to discontinue warfarin Our group has had a very low stroke risk, even in patients with high CHADS2 scores, using this approach.24

SURGICAL RESULTS

The Cox-Maze procedure has been the gold-standard treatment for the surgical ablation of AF over the last two decades and has the single highest success rate of any interventional procedure in terminating ATAs At our institution, 198 patients receiving the traditional cut-and-sew Cox-Maze III procedure had a 97% free-dom from symptomatic AF at 5.4 years There was no difference in recurrence in patients receiving a stand-alone Cox-Maze III compared with patients receiving

a concomitant procedure.18 Unfortunately, at most centers, few patients with AF received a concomitant Cox-Maze III procedure during cardiac surgery because of the associated long cross-clamp times This practice has changed with the adop-tion of ablation technology and the Cox-Maze IV, with over 40% of AF patients receiving a concomitant Cox-Maze IV in 2006.19

The efficacy of the Cox-Maze IV procedure has been reported Our group prospectively followed 100 patients receiving a stand-alone Cox-Maze IV with scheduled follow-ups at 3-, 6-, and 12-month intervals and annually thereafter using at least 24-hour Holter monitoring in the majority of patients Procedural failure was defined as any ATA lasting longer than 30 seconds This study had a mean follow-up time of 17 ± 10 months and 69% of patients had either persistent

or longstanding persistent AF At both 1 and 2 years, 90% of patients were free from ATAs, with 82% of patients also free from ATAs off antiarrhythmic medica-tions.27 A follow-up study compared the Cox-Maze IV population retrospectively with 112 patients who had a Cox-Maze III procedure In the Cox-Maze III group, late recurrence was determined by freedom from symptomatic AF at follow-up, which likely overestimated procedural success This comparison showed no signif-icant difference in freedom from AF off antiarrhythmic medications between the Cox-Maze IV and Cox-Maze III procedures (83% vs 82%).22

Although freedom from AF was similar for the Cox-Maze III and

Cox-Maze IV procedures, the Cox-Maze IV has been shown to have several

peri-operative advantages Mean aortic cross-clamp times for the Cox-Maze IV were

significantly decreased for both the stand-alone Cox-Maze IV (41 ± 13 minutes

vs 93 ± 34 minutes) and concomitant Cox-Maze IV procedures (93 ± 29 minutes

vs 122 ± 37 minutes).18,27,28 A comparison of the Cox-Maze III and Cox-Maze IV

also showed a significant decrease in major morbidity among patients receiving a

Cox-Maze IV.22 This same series showed that there were no differences in 30-day

mortality or postoperative stroke when comparing these two approaches

The introduction of the minimally invasive RMT approach has further

decreased the complication rates while preserving efficacy A comparison of these

two approaches in over 350 patients showed no difference in freedom from ATAs

off antiarrhythmic medications at 2 years (Figure 9.5) However, the patients who

underwent RMT had fewer complications, decreased ICU stay, and decreased

median length of hospital stay when compared with those patients who received

a sternotomy approach.29

Risk factors for the recurrence at 1 year include: (1) failure to perform

a “box lesion”; (2) increasing left atrial size; and (3) early ATAs The original

Cox-Maze IV lesion set did not contain a box-lesion because it did not include

the connecting lesion between left and right superior PVs Initially, there was

a concern that complete posterior LA isolation would have detrimental effects

on atrial function However, this has been disproven in experimental work in

our laboratory using cardiac MRI.30 The addition of this lesion, which completed

isolated the posterior LA, resulted in a dramatic increase in freedom from ATAs

off antiarrhythmic medications (85% vs 47%) at 1-year follow-up 27 Increasing

LA size has been shown to be a risk factor for recurrence among multiple studies,

ATAs were previously shown by our group to be a risk factor for recurrence and are likely a marker of advanced pathology.32

Several groups have reported minimally invasive approaches with more ited lesion sets.35–38 However, there are few reports detailing the late outcomes of these approaches In brief summary, the results generally have been worse with more limitted lesion sets The use of PV isolation alone has been fraught with a high incidence of late recurrence with a less than 50% success rate at 2 years in our experience Because of these poor results, the use of PV isolation alone is discouraged, particularly in patients with concomittant cardiac disease or who have persistent AF

lim-Recently, hybrid procedures have been introduced combining both cardial and epicardial ablation.39 Although early experience in highly selected patients has been encouraging, the late results are still unknown The efficacy of epicardial ablation is still limited by the inability of present ablation devices to reliably create transmural ablation lines on the beating heart.40 These procedures should be performed only in specialized centers that have expertise in both cath-eter and surgical ablation and a commitment to careful follow-up

endo-CONCLUSION

The surgical treatment of AF has gone through considerable evolution over the last decade because of advancements in both minimally invasive and ablation technologies The role of minimally invasive approaches will likely continue to grow as procedures become more standardized and technologies improve The ideal surgical treatment for AF would consist of a patient-tailored lesion set using devices that consistently achieved 100% transmurality through a mini-mally invasive approach without the need for CPB To achieve this goal, more research is needed to better understand the mechanisms of AF, particularly

in patients with accompanying organic heart disease There is also a ling need to develop more effective tools for epicardial ablation Until then, the minimally invasive CMIV is able to restore sinus rhythm in over 90% of patients with very low morbidity and is the procedure of choice in the majority of patients

compel-ACKNOWLEDGMENT

Funding provided in part by National Institute of Health under Grants T32 HL007776 and RO1 HL03225 R.J.D is a consultant for AtriCure, and has received research and educational funding from AtriCure and Edwards

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With the prevalence of atrial fibrillation (AF) predicted to exceed 12 million cases

in the United States by 2030, electrical cardioversion and AF ablation procedures

will likely comprise a major portion of procedural volume in most labs.1 Clinical

electrophysiology has undergone a dramatic transformation over the past several

decades Once limited to simple diagnostic procedures, the electrophysiology

lab (EPL) has evolved into an interventional suite where intricate and complex

therapies are performed on a daily basis Radiofrequency ablation for AF is

among the most technically demanding procedures now performed in the EPL

Electrical cardioversions have become a daily fixture in the lab To meet the

clini-cal demands of these procedures, the need for anesthesiology expertise in the EPL

is instrumental This chapter is devoted to summarizing published current best

practices in the delivery of anesthesia care to patients being treated with direct

current cardioversion or radiofrequency ablation for AF

PREANESTHESIA EVALUATION

Patient History

A standard set of information should be collected and documented during the

preanesthesia evaluation (Table 10.1) This initial evaluation should always begin

with a comprehensive history and physical examination A current and detailed

note including the indication for the procedure should be completed by the

elec-trophysiology team and be available at the time of evaluation by the anesthesia

care team (ACT) The history-taking process should be devoted to eliciting a

complete past medical history, obtaining an accurate medication list (including

medications taken and not to be taken the day of procedure), confirming allergies

(including latex or heparin) and NPO status Timing of the last β-blocker dose,

use of antiarrhythmic medications, and anticoagulation status require special

Anesthesia Care for the Atrial Fibrillation Patient: Cardioversion and AF Ablation

Alfred J Albano, MD, Zachary Camann, MD, and Michael England, MD

Atrial Fibrillation: A Multidisciplinary Approach to Improving Patient Outcomes © 2015

Joseph S Alpert, Lynne T Braun, Barbara J Fletcher, Gerald Fletcher, Editors-in-Chief,

Cardiotext Publishing, ISBN: 978-1-935395-95-9

attention Patients should also be asked about prior adverse anesthetic ences and/or difficulties with intubation or malignant hyperthermia A history of postoperative nausea and vomiting (PONV) as well as other risk factors should routinely be elicited, so prophylactic antiemetics can be considered.2

experi-A comprehensive understanding of patients’ comorbidities is critical to ensure appropriate periprocedural management and minimize complications In the unusual circumstance that objective data on cardiac function is unavailable, this can be grossly assessed by asking about functional capacity The ability to climb

a flight of stairs without dyspnea corresponds to approximately 4 METS Patients

Ta b le 1 0 1

Pre-Anesthesia Evaluation

ASA Guidelines for Documentation of Care

Patient History

• Patient and procedure identification

• Verification of admission status

who smoke or have pulmonary disease including obstructive sleep apnea are at

higher risk for respiratory complications The “STOP-Bang” questionnaire (loud

snoring, tiredness during the daytime, observed apneas, high blood pressure,

body mass index (BMI) > 35 kg/m2, over 50 years of age, neck circumference

> 40 cm, and male gender) is a simple tool that can be used to quickly assess for

underlying obstructive sleep apnea (OSA).3 Those with renal or hepatic

dysfunc-tion may require medicadysfunc-tion dosage adjustments and may be precluded from

receiving certain medications Type 2 diabetic patients should be counseled not

to take their morning insulin or oral hypoglycemic agents on the day of the

pro-cedure and will need to have their glucose monitored and controlled if necessary

with short-acting insulin Type 1 diabetics may need to take one-third to one-half

of their morning intermediate or long-acting insulin, as diabetic ketoacidosis may

develop if medication is held They should be educated on recognizing signs and

symptoms of hypoglycemia that may occur prior to entering a healthcare

facil-ity If that occurs, oral consumption of a clear liquid glucose-containing solution

(50–100 mL) may be necessary Medical consultations may be necessary to assist

in the risk stratification and medical optimization of particularly challenging

patients with multiple comorbidities Subspecialty consultants should help assess

whether the patient’s comorbidities are optimally treated and recommend specific

therapies to decrease the risk of periprocedural complications

Physical Examination

In addition to the patient history, a thorough physical examination should be

per-formed, noting vital signs (including bilateral upper extremity blood pressures)

and evaluating the airway Height, weight, and BMI should be documented The

Mallampati classification system is commonly used among anesthesiologists to

predict the ease of intubation This was originally described in 1985 as a

three-class system but then modified by Samsoon and Young in 1987 to include four

anatomical landmarks: the soft palate, fauces, uvula, and pillars (Figure 10.1)

A patient with a class I oropharynx has all four landmarks visible In class II,

the soft palate, fauces, and uvula are visible In class III, only the soft palate and

base of the uvula can be seen, whereas in class IV the entire soft palate is not

visible.4,5 A favorable modified Mallampati class (class I) does not always predict

an easy intubation, nor is an unfavorable modified Mallampati class (class IV)

always predictive of difficulty In fact, a recent meta-analysis determined that

the Mallampati test itself had poor to moderate discriminative power when used

alone in this regard.6 However, this method of airway evaluation is commonly

and widely used as an initial tool in alerting the ACT that there might be an

airway issue

The value of the Mallampati score can be improved by considering it in junction with other predictors of difficult intubation These factors include: small mouth opening (a narrow inter-incisor distance), limited jaw mobility (an inabil-ity to push the lower jaw forward over the upper jaw), limited head extension, and a thyromental distance of less than 7 cm.7 Poor dentition can be a risk factor for dental damage during laryngoscopy, and certain patterns of dentition such as overhanging central incisors can make intubation challenging This is especially important if the location of the procedure is “off site” as there may be a delay in getting assistance in a timely fashion The American Society for Anesthesiology (ASA) has standardized the algorithm for managing anticipated and unantici-pated difficult airways.8

con-The risk factors that predict difficult intubation are different from those that predict difficult ventilation with a face mask Predictors of difficult mask

Fig u r e 1 0 1

Anatomy of the posterior oropharynx

ventilation include obesity, increased neck circumference, advanced age, upper

airway obstruction (as in sleep apnea), limited mandibular protrusion, and the

presence of facial hair A laryngeal mask airway (LMA) is an invaluable tool in

the anesthesiologist’s airway armamentarium for both elective and rescue use in

a situation where the patient cannot be intubated or ventilated Aids to intubation

should be readily available and close at hand during any induction of anesthesia

so the anesthesiologist may be prepared for any complications that may ensue

In addition to an LMA, the use of an oro- or nasopharyngeal airway, a video

laryngoscope [either disposable units made by AIRTRAC® and King Systems or

reusable devices made by Verathon®(Glidescope), Teleflex® (McGrath), and Storz®

(C-MAC)], or a flexible fiberoptic bronchoscope may prove invaluable in the

set-ting of a difficult airway (Figure 10.2) Being well prepared is the key to avoiding

an airway disaster

An important part of the preanesthesia evaluation is the determination of

the ASA physical status The ASA physical status classification was introduced in

1940 as a global assessment of the patient’s state of health (Table 10.2) The values

range from 1 to 6, with 1 denoting a healthy patient and 6 indicating a brain-dead

organ donor Importantly, an ASA class of 5 describes a moribund patient who is

not expected to survive with or without the procedure An “E” designation may

be added for emergency cases whereby delaying the case (in cases of a recent meal

or liquids of any quantity) would not be appropriate, especially in a patient with

unstable hemodynamics The utility of the ASA physical status is that it clearly

communicates an anesthesiologist’s prediction of morbidity and mortality based

on a comprehensive evaluation of the patient’s current condition This

classifica-tion can also be used to stratify patients for outcomes-related data analyses

Review of Diagnostic Studies

Objective laboratory data, radiographic studies, prior cardiac testing, previous

electrophysiology procedures, and prior surgeries (noting any previous difficulty

by a former ACT) should also be carefully reviewed Special attention should be

devoted to the patient’s renal and hepatic function, serial coagulation studies, the

baseline 12-lead electrocardiogram (ECG), and recent echocardiography exams

(including transesophageal studies) if performed In accordance with the 2011

ACC/AHA guidelines, patients with AF of an unknown duration or > 48 hours

undergoing direct current cardioversion should have weekly INRs ≥ 2 for 3 weeks

prior to cardioversion.9 Alternatively, a TEE excluding left atrial appendage

throm-bus can be performed to eliminate the need for 3 weeks of anticoagulation or those

patients having difficulty achieving 3 weeks of weekly therapeutic INRs In patients

with an elevated CHA2DS2-VASc score, particularly those with heart failure and

Fig u r e 1 0 2

Intubation aids for challenging airways A: Laryngeal Mask Airway B: Intubation Tray (top to bottom: Nasopharyngeal Airway, Endotracheal Tube, and Laryngeal Mask Airway) C: Flexible Fiberoptic Scope D: Video Laryngoscope

A

B

Ta b le 1 0 2

American Society of Anesthesiology Classification of Physical Status

Physical Status Description

2 Mild systemic disease without functional limitation

3 Severe systemic disease with functional limitation

4 Life-threatening, severe systemic disease

5 Moribund, not expected to survive operation

48 hours.10 The use of TEE should therefore be considered in this high-risk patient population Patients with a history of atrial thrombus should be anticoagulated for 4 to 6 weeks and have demonstrable resolution of clot on a repeat TEE before attempting cardioversion The ECG should be carefully analyzed for the presence

of conduction system disease, ST-T wave abnormalities, and QTc prolongation

A chest radiograph should be obtained to assess for occult pulmonary disease, evaluate positioning of any devices, and establish a baseline measurement for the cardiac silhouette When a patient’s functional capacity is ambiguous, a direct assessment of LV function using transthoracic or transesophageal echocardiogra-phy should be performed if such testing has not been done already

Formulation of the Anesthetic Plan

The goal of anesthesia is to maintain patient comfort and a quiet procedural field through a combination of agents producing anxiolysis, amnesia, and analgesia The extent of the procedure and the physical status of the patient should always

be taken into consideration when formulating the anesthetic plan In addition,

it is important to note that levels of sedation (Table 10.3) are a continuum, and inadvertent administration of an excessive dose of medication may risk airway compromise Thus, any plan to sedate a patient must include contingencies for intensive and advanced airway management should general anesthesia become necessary The North American Society of Pacing and Electrophysiology con-sensus document states that anesthesia personnel should be involved in all EPL

Ta b le 1 0 3

Levels of Anesthesia Sedation

Minimal Sedation (Anxiolysis) Moderate Sedation (Analgesia) Sedation (Analgesia) Deep General Anesthesia Responsiveness

Normal response

to verbal stimulation

Purposeful response to verbal or tactile stimulation

Purposeful response following repeated

or painful stimulation

Unarousable even with painful stimulus

Airway Unaffected No intervention required Intervention may be required Intervention often requiredSpontaneous