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ELECTROPHYSIOLOGY

ORIGINAL ARTICLES

Assessing the Immediate andSustained Effectiveness of CircularEpicardial Surgical Ligation of the LeftAtrial AppendageCorey Adams, M.D.,∗ Daniel Bainbridge, M.D.,† Aashish Goela, M.D.,‡ Ian Ross, M.D.,‡and Bob Kiaii, M.D.∗

∗Division of Cardiac Surgery, Department of Surgery; †Department of Anesthesiology andPerioperative Medicine; and ‡Department of Radiology, University of Western Ontario,London Health Sciences Centre, London, Ontario, Canada

ABSTRACT Background/Aim: Obliterating the left atrial appendage from systemic circulation in patients with

atrial fibrillation has been proposed to reduce thromboembolic events. The goal of this study was to assess

the effectiveness of a circular method of epicardial surgical ligation in obliterating the left atrial appendage

and maintaining sustained exclusion. Methods: Patients with permanent atrial fibrillation and an indication

for elective cardiac surgery were enrolled. All patients underwent preoperative cardiac gated computerized

tomography (CT) and transesophageal echocardiography (TEE). During the cardiac procedure circular lig-

ation of the appendage was performed. Results: Twelve patients, mean (SD) age 65 (12) years completed

the study. Intraoperative TEE demonstrated all patients (12/12) had complete postligation occlusion of the

left atrial appendage. At three-month follow-up, cardiac gated CT demonstrated that 75% (9/12) of the

patients had communication of contrast dye from the left atrial appendage to body of left atrium. Left

atrial appendage orifice area and volume were reduced from mean (SD) (5.5 cm2 [1.8] to 0.5 cm2 [0.4]

p = 0.002) and (14.0 cm3 [8.3] to 2.7 cm3 [1.3] p = .005) postligation, respectively. No clinically significant

thromboembolic events were reported. Conclusions: Epicardial suture ligation of the left atrial appendage

resulted in successful intra-operative exclusion on TEE; however, a significant portion of patient’s demon-

strated communication of contrast on CT. This is suggestive of incomplete long-term exclusion. The clinical

significance of reduction in left atrial appendage orifice area and volume with a persistent communication

requires further study. doi: 10.1111/j.1540-8191.2012.01422.x (J Card Surg 2012;27:270-273)

The left atrial appendage (LAA) is the most commonsite for intracardiac thrombus in patients with persis-tent atrial fibrillation.1 The LAA can easily be excludedfrom systemic circulation at the time of cardiac surgeryand it is postulated that doing so may reduce the riskof future thromboembolic events.2-3 However, variablesuccess rates for complete occlusion have been re-ported and therefore the clinical benefit of reduction

Conflicts of interest: The authors have no financial or commercialinterest in the manufacturer or distributor of the product, including anycorporate funding or affiliations.

Funding: No funding was required for completion of this study.

Address for correspondence: Bob Kiaii, M.D., Division of CardiacSurgery, Department of Surgery, London Health Sciences Centre,University Hospital, 339 Windermere Road, London, ON N6A 5A5,Canada. Fax: 519-663-3044; e-mail: Bob.kiaii@lhsc.on.ca

in thromboembolic events has not been clearly es-tablished.4-5 Incomplete closure of the LAA may ac-tually increase the risk of future embolization.5-6 Cur-rently, the best practice technique for occlusion of theLAA remains unknown and techniques such as liga-tion, oversewing from the inside, stapling, amputa-tion, and epicardial suture ligation are all commonlyperformed.4,6,7 There remains a need to objectivelyassess and quantify the surgical techniques used forLAA ligation. The objective of this study was to as-sess, via transesophageal echocardiography (TEE) andcardiac gated computed tomography (CT), the effec-tiveness of a circular epicardial surgical ligation in im-mediately obliterating the LAA and maintaining occlu-sion at three-month follow-up. Secondary objectiveswere to describe the changes in LAA orifice cross sec-tional area and volume postligation as a risk factor forsystemic thromboembolic events. This study will add

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to the current body of literature regarding the potentialrole for cardiac gated CT in assessing LAA ligation.

MATERIALS AND METHODS

This was a single-center, single-surgeon, observa-tional study. Following institutional review board ap-proval and obtaining written patient informed con-sent, consecutive patients referred for cardiac surgicalprocedures (coronary artery bypass grafting surgery,and/or mitral valve surgery) were assessed for enroll-ment. Inclusion criteria included patients with a knownhistory of permanent atrial fibrillation (atrial fibrillationthat has persisted for more than one year, requiringpharmacological treatment for a rate control with an-ticoagulation strategy) and scheduled to undergo anelective cardiac surgical procedure. All patients under-went preoperative cardiac gated CT scanning and TEE.Exclusion criteria were a broad-based LAA on preoper-ative cardiac gated CT scan or TEE and/or documenta-tion of prior LAA thrombus. At time of the operation,all patients underwent a midline sternotomy and on-pump cardiopulmonary bypass techniques. Intraopera-tively, all patients underwent TEE by a single board cer-tified anesthesiologist. Upon commencing cardiopul-monary bypass, all patients underwent ligation of theLAA using the Endoloop c© suture ligature (Johnson &Johnson, Cincinnati, OH, USA). The Endoloop c© is an0-polypropelyne, monofilament suture ligature, whichis positioned across the base of the LAA and tightenedby the surgeon. The LAA was grasped with a non-traumatic clamp, and the Endoloop c© snare was ma-nipulated to the base of the appendage and cincheduntil it was occluded. All patients underwent a sin-gle application of the Endoloop c© device. No immedi-ate complications occurred with ligation. Intraoperativetwo-dimensional (2D) color TEE was performed whenoff cardiopulmonary bypass and successful obliterationwere confirmed by the absence of blood flow betweenthe body of left atrium and the LAA. The remaining as-pects of the ongoing cardiac procedure and postoper-ative convalescence were completed without modifi-cation. All patients resumed their previous anticoagu-lation regimen for atrial fibrillation following the cardiacprocedure. Patients had a follow-up cardiac gated CTheart at three months from the date of operation. Twopatients for other clinical indications also underwentpostoperative TEE after three months. The primary out-come measure of the study was assessment of com-munication via contrast dye between the LAA and bodyof the left atrium on CT scan at three-month follow-up.A successful ligation was defined as exclusion of allintravenous contrast between the LAA and the bodyof the left atrium. Secondary outcomes included pre-and postligation measurements of the LAA orifice areaand LAA volume. A Student’s t-test was used to as-sess LAA cross-section orifice area and volume pre-and postligation with p values less than or equal to 0.05considered statistically significant. All patients were as-sessed at three-month follow-up for thromboembolicevents such as cerebrovascular accident, transient is-

chemic attacks, and peripheral arterial embolic events.Medical records from any of the patient’s hospitaliza-tions since the operation were reviewed.

RESULTS

Twelve patients (eight males and four females) withmean (SD) age of 64 (12) years with permanent atrialfibrillation were enrolled and completed the study. Nopatients were excluded for either a broad-based ap-pendage or identification of intra-cardiac thrombus.Cardiac procedures included isolated coronary arterybypass surgery (CABG) n = 2; isolated mitral valve re-placement n = 5; combined mitral replacement andCABG surgery n = 5. No patients were identified ascandidates to undergo a surgical ablation procedure toaddress atrial fibrillation. Intra-operative TEE confirmedligation with absence of color flow on 2D Doppler post-LAA ligation with Endoloop c© (Johnson & Johnson) onsingle application in all 12 patients (100% successfuldeployment). No additional TEE measurements otherthen absence or presence of flow postligation wererecorded. No intra-operative complications, such asatrial tears or excessive bleeding, occurred during liga-tion. All patients had an uncomplicated hospital coursewith no early or late mortalities. Previous medicationand anticoagulation strategies were resumed for all pa-tients postcardiac procedure. All patients returned atthree months from the date of surgery for follow-upcardiac gated CT. The primary outcome demonstratedthat nine of the 12 patients (75%) had communica-tion of contrast dye between the LAA and the bodyof the left atrium. Figure 1A and B shows CT heart of2D image pre- and postunsuccessful complete ligation.In addition, two patients had postoperative TEE beyondthree months and both were found to have an openLAA with one patient showing evidence of thrombusin the LAA. Both of these patients had an open LAA ontheir postoperative CT scans.

Secondary outcomes demonstrated a statisticallysignificant reduction in LAA orifice area from preliga-tion mean (SD) 5.5 cm2 (1.8) to postligation mean (SD)0.5 cm2 (0.4), p value = 0.0002; LAA volume was statis-tically significantly reduced from preligation mean (SD)14.0 cm3 (8.3) to postligation 2.7 cm3 (1.3), p value =0.005 (Table 1). At three-month follow-up, no patientshad evidence of a thromboembolic event as assessedby clinical examination and review of medical hospital-izations. Review of medical documents demonstratedthat seven of 12 patients had a postoperative transtho-racic echocardiogram (TTE), of which the LAA was notseen in five of those. Two patients had postoperativeTEE beyond three months and it was identified in bothfor the LAA to be widely patent; in one patient, therewas evidence of thrombus in the LAA. The patientsidentified as having a patent LAA on TTE demonstratedfailed occlusion on CT follow-up. In addition, the twopatients who had a TEE at three-month postoperationfor a clinical indication also had a failed occlusion of theLAA on their CT. We retrospectively reviewed theseTEE images, and in one patient the LAA was widely

272 ADAMS, ET AL.LEFT ATRIAL APPENDAGE LIGATION

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Figure 1. (A) CT heart of 2D image of left atrial appendagebefore ligation. (B) CT heart of 2D image of left atrial ap-pendage postligation at three months demonstrating com-munication between atrium and left atrial appendage.

TABLE 1

Cardiac Gated CT Measurements of Left Atrial

Appendage Orifice Cross-Section Area and

Volume Pre- and Postligation (Mean [SD], 95%

confidence interval), p Value

Orifice Cross-Sectional Appendage

Area (cm2) Volume (cm3)

Preligation 5.5 (1.8) 14.0 (8.3)Postligation 0.5 (0.4) p = 0.0002

(4.2 to 6.7)2.7(1.3) p = 0.005(8.3 to 19.7)

patent with a LAA neck size of 0.8 cm, presence ofthrombus within in the LAA and an LAA measurementof 0.39 cm2 × 2.5 cm2. This patient demonstrated afailed long-term occlusion on CT follow-up. The secondpatient was noted to have thrombus in the neck of theLAA and a LAA measurement of 2.3 cm2 × 1.6 cm2.

CONCLUSIONS

This study demonstrated that despite 100% suc-cessful intra-operative occlusion of the LAA asdetected by the intra-operative 2D color Doppler TEE,75% of patients demonstrated communication of dyebetween the LAA and the left atrium at three-monthfollow-up on cardiac gated CT. This high incomplete oc-clusion rate at long-term follow-up from an epicardialsuture ligation technique may have important clinicalimplications.

There are several possible explanations for the in-ability to maintain long-term obliteration of the LAA.First, the application of the circular ligature may havebeen technically inadequate. The suture ligature maynot have been placed deep enough on the base of theLAA because of concern regarding the left circumflexcoronary artery in the atrioventricular groove, whichcan inadvertently be injured. Second, edema of theLAA, which may occur while on cardiopulmonary by-pass, may resolve over time. This would allow the re-establishment of a connection between the body ofthe atrium and the LAA after the edema subsides. Fi-nally, our results may reflect a difference in the sensi-tivity of differing modalities used to assess short, andlong-term occlusion of the LAA. Cardiac gated CT ofthe heart may be too sensitive in detecting a commu-nication. One of the weaknesses of the study is thatwe did not assess LAA occlusion patients immediatelypostoperatively with cardiac gated CT heart. Therefore,we are unable to know if there was a degree of com-munication present immediately postligation or if thisdeveloped over time. We also did not repeat a follow-upTEE to assess long-term closure via the same modality,due to the inconvenience it created for patients. Ret-rospectively, we obtained TEE images from only twopatients who underwent this imaging for a nonstudy-related indication. This revealed a widely patent LAAand thrombus at the neck of the LAA in one and in thebody of LAA in the other. Inferences based on thesetwo patients cannot be made but both patients werein the cohort that demonstrated failed long-term oc-clusion, suggesting a possible correlation. It would berelevant to compare measurements of TEE and CT pre-and postligation in effort to predict the likelihood of asustained occlusion.

Results of this study agree with previously publishedreports regarding variable rates of successful occlu-sion of the LAA regardless of the surgical techniqueused.4,7-9 The highest reported success rate in largemeta-analysis was 93%; however, most studies re-ported success rates of only 55% to 66% when us-ing closure techniques including stapling, ligation, andamputation.4,7-9 The Left Arial Appendage OcclusionStudy (LAAOS), which used a similar epicardial suturetechnique as our study, detected a sustained rate ofclosure on postoperative TEE of only 45% (5/11).7 Al-though we report a sustained rate of only 17% as de-tected on cardiac gated CT just three months postop-eratively. It is difficult to compare our lower rate ofsustained occlusion with those obtained in previousstudies as we utilized cardiac gated CT for assessment

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of sustained occlusion compared to more often uti-lized modality of TEE. To date the sensitivity and speci-ficity of TEE in comparison to cardiac gated CT heartin detecting complete LAA ligation has not been per-formed. Therefore, we suggest the importance of con-sidering both the surgical technique and postligationimaging modality when assessing LAA occlusion out-comes. The sensitivity of different imaging modali-ties may differ and therefore lead to different report-ing rates for successful occlusion. This study raisesimportant questions regarding the role of successfulintra-operative TEE in detecting sustained occlusion ifin fact cardiac gated CT heart is more sensitive. Fur-thermore, the role for intra-operative three-dimensional(3D) TEE in assessing LAA ligation should be furtherstudied and compared to various other imaging modal-ities. 2D color Doppler should be compared to newermodalities such as 3D TEE assessment.

Another important finding of this study is the clini-cal relevance of the continued contrast on CT betweenthe LAA and the body of the left atrium despite signif-icant reduction in LAA orifice cross-sectional area andvolume. The significant reduction in the LAA cross-sectional orifice area may decrease the likelihood forthrombus to migrate through the orifice and subse-quently reduced thromboembolic events. However, anincomplete occlusion of the LAA that has reducedthe LAA volume may actually result in an increase inthe amount of stagnant blood flow and thus potenti-ate thrombus formation. At three-month follow-up wereported no patients experiencing a thromboembolicevent; a much larger sample size of patients followedfor a longer period of time would be required to as-sess the clinical relevance of the reduction of the LAAcross sectional orifice and volume detected on car-diac gated CT. The current level of evidence regard-ing the reduction of thromboembolic embolic eventswith LAA ligation does not support discontinuing an-ticoagulation in patients with permanent atrial fibril-lation. A larger population-based study would be re-quired to assess this important clinical decision. There-fore, we continued anticoagulation in all our patientspostligation.

Despite its limitations, we feel this study has im-portant clinical results. First, circular epicardial sutureligation of the LAA, while causing a decrease in orificearea and appendage volume, does not appear to main-tain complete obliteration of the LAA at three-month

follow-up as assessed by cardiac gated CT. On the ba-sis of the clinical results of this study we are no longerusing an epicardial suture ligation technique for LAA.Our current technique is directly amputating the ap-pendage from the outside and then oversewing theopening with a running polypropylene suture. Second,important questions are raised regarding the diagnos-tic accuracy of different imaging modalities used to as-sess LAA occlusion. Clinical correlation between out-comes of cardiac gated CT such as reduction in LAAcross-sectional area and volume should be examined toassess the utilization of these outcomes in assessingsuccessful LAA ligation.

REFERENCES

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