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

c h a pt e r

8

Left Atrial Appendage Excision,
Ligation, and Occlusion Devices
Taral K. Patel, MD, and Bradley P. Knight, MD

ATRIAL FIBRILLATION AND STROKE
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 mechanical dysfunction in the atria, leading to impaired blood flow and stasis. AF also
promotes endothelial dysfunction, inflammation, platelet activation, and hypercoagulability, 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 impressive 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 surface 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

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

 

 

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The LAA, because of its complex anatomy, innumerable potential spaces,
and low blood flow during AF, is particularly susceptible to thrombus formation.
Studies using magnetic resonance imaging (MRI) and transesophageal echocardiography (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 extensive meta-analysis.16
However, the widespread use of systemic anticoagulation has highlighted
several important limitations of this strategy. Most importantly, systemic anticoagulation unavoidably increases bleeding risk. Up to 40% of AF patients have
relative or absolute contraindications to anticoagulation, usually owing to a history 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 HASBLED 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 medications. 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
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


 Chapte r 8 LAA Excisio n, Lig atio n, and Occlusio n De vice s

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 interactions 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 fundamental 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 procedure 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, substantial 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 Madden 24 published
a case series of 2 patients who underwent LAA removal as a prophylaxis for recurrent 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 anticoagulation and demonstrated comparable stroke rates during follow-up.27 The results

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pave the way for a larger trial to answer the critical question of whether surgical

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 titanium 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 largest 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
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 thoracotomy, 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


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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.

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% compared favorably with the CHADS2-predicted rate of 6.3%. A North American registry 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


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A

B

Fig u r e 8 .2
(A) The WATCHMAN device 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.


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Fig u r e 8 .3
Fluoroscopic image of the WATCHMAN device (arrow) deployed in the left atrial appendage.

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


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To date, this study represents the only randomized trial comparing LAA exclusion 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 anticoagulation. The trial was designed to test noninferiority of WATCHMAN to standard warfarin therapy. After 1065 patient-years, the primary efficacy end point
(stroke, systemic embolism, or cardiovascular or unexplained death) was superior
in the WATCHMAN arm versus the warfarin arm (3.0% vs. 4.9% per 100 patientyears), 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
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 efficacy 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 regarding 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 randomized 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 eventual FDA approval.


 Chapte r 8 LAA Excisio n, Lig atio n, and Occlusio n De vice s

Fig u r e 8 .4
Transesophageal echocardiographic image of a thrombus (arrow) on a WATCHMAN device
several months after anticoagulation was discontinued.

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 warfarin, reduction in bleeding complications, and elimination of dietary and drug
interactions.38

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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 product 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 complications occurred (one device embolization and one cardiac tamponade). TEE at
6 months showed a disappointing 16% rate of peri-device leak, but 20-month follow-up demonstrated no incidence of device-related death or thromboembolism.
Importantly, ACP implantation protocols have generally not involved periprocedural anticoagulation, instead employing dual antiplatelet therapy for one
month followed by aspirin monothereapy. Concerns remain about the incidence
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 exclusion 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 closure is not satisfactory, the snare can be repositioned prior to irreversible suture
release (Figure 8.7).

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119

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.


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Fig u r e 8 .6
Major components of the LARIAT system, including magnet-tipped guidewires, endovascular
balloon catheter, and a pre-tied suture mounted to an epicardial snare. Source: Image courtesy
of SentreHeart, Inc.

Fig u r e 8 .7
Fluoroscopic sequence of the LARIAT procedure. (A) After transseptal and pericardial
access, baseline left atrial angiography identifies the left atrial appendage. (B) Magnettipped 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.

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This hybrid approach offers several theoretical advantages, including complete 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 variables 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 experience 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 pericarditis, 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 pericardial 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

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source of the majority of thromboembolism in AF. Exclusion of the LAA is naturally 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 longterm 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 success 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.
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 endovascular 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 alternative 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 superiority 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.


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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 strategy 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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predicting stroke and thromboembolism in atrial fibrillation using a novel risk factor-based
approach: The euro heart survey on atrial fibrillation. Chest. 2010;137(2):263–272.
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in patients who have nonvalvular atrial fibrillation. Ann Intern Med. 2007;146(12):857–867.
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Brass LM, Krumholz HM, Scinto JM, Radford M. Warfarin use among patients with atrial
fibrillation. Stroke. 1997;28(12):2382–2389.
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Walker AM, Bennett D. Epidemiology and outcomes in patients with atrial fibrillation in
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Granger CB, Alexander JH, McMurray JJ, et al. Apixaban versus warfarin in patients with

atrial fibrillation. N Engl J Med. 2011;365(11):981–992.
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fibrillation. N Engl J Med. 2009;361(12):1139–1151.
Patel MR, Mahaffey KW, Garg J, et al. Rivaroxaban versus warfarin in nonvalvular atrial
fibrillation. N Engl J Med. 2011;365(10):883–891.
Madden J. Resection of the left auricular appendix: A prophylaxis for recurrent arterial
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a report of the American College of Cardiology/American Heart Association Task Force
on Practice Guidelines (Writing Committee to revise the 1998 guidelines for the management of patients with valvular heart disease). Endorsed by the Society of Cardiovascular
Anesthesiologists, Society for Cardiovascular Angiography and Interventions, and Society
of Thoracic Surgeons. J Am Coll Cardiol. 2008;52(13):e1–e142.
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novel device: Early results of a multicenter trial. J Thorac Cardiovasc Surg. 2011;142(5):1002–
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versus warfarin therapy for prevention of stroke in patients with atrial fibrillation: A randomised non-inferiority trial. Lancet. 2009;374(9689):534–542.
Reddy VY, Doshi SK, Sievert H, et al. Percutaneous left atrial appendage closure for stroke
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(Watchman Left Atrial Appendage System for Embolic Protection in Patients with Atrial
Fibrillation) Trial. Circulation. 2013;127(6):720–729.
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the AMPLATZER cardiac plug device in patients with nonvalvular atrial fibrillation and
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c h a pt e r

9

Atrial Fibrillation: A Surgical
Approach to Improving
Patient Outcomes
Christopher P. Lawrance, MD, and Ralph J. Damiano, Jr., MD

INTRODUCTION
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) palpitations, which cause patient discomfort and anxiety; (2) loss of synchronous
atrioventricular (AV) contraction, compromising cardiac hemodynamics, resulting 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 goldstandard surgical treatment for AF, the Cox-Maze (CM) procedure. In 1980, Dr.

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

 

 

127


128   Se ct io n 1: At ria l Fib rilla t io n : Ba ckg ro u n d , Eva lu a t io n , a n d Ma n a g e m e n t

However, because the electrically isolated LA remained in AF, the procedure did
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 refractory 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 introduced 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 responsible 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
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


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129

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.

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 receiving cardiac surgery also received a Cox-Maze III operation.19 Advances in ablation technology have revolutionized 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-andsew” 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


130   Se ct io n 1: At ria l Fib rilla t io n : Ba ckg ro u n d , Eva lu a t io n , a n d Ma n a g e m e n t

Fig u r e 9 .2
Bipolar radiofrequency ablation Cox-Maze IV schematic.

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 sternotomy which is described below. However, advances in minimally invasive surgery
have allowed the procedure to be performed through a (5–6 cm) right minithoracotomy (RMT) in most patients.25,26 Contraindications to this approach include
patients with severe respiratory disease, previous right thoracotomy, or aortoiliac


 Chapte r 9 Atrial Fibrillatio n: A Surg ical Appro ach

 

disease. The RMT is performed using single-lung inflation and femoral cannulation 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 intraoperative 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 ablations 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 sternotomy 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 confirmed 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 appendage (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 superior 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 maintaining the fibrous structure and integrity of the annulus and valvular tissue, as

131


132   Se ct io n 1: At ria l Fib rilla t io n : Ba ckg ro u n d , Eva lu a t io n , a n d Ma n a g e m e n t

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.

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 anterograde cold-blood cardioplegia is administered. With the heart arrested, the left
atrial appendage (LAA) is amputated. Through this incision, one jaw of the bipolar 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 arterial circulations. A standard horizontal left atriotomy is performed and can be
extended superiorly onto the dome of the LA or inferiorly around the right inferior 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
is performed by sequential endocardial cryoablations behind the left PVs, connecting 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


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133

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.

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 arrhythmias 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