Summary

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was ‘Should patients undergoing cardiac surgery with atrial fibrillation (AF) have left atrial appendage (LAA) exclusion?’ Altogether 310 papers were found using the reported search, of which 12 represented the best evidence to answer the clinical question. The authors, journal, date and country of publication, patient group studied, study type, relevant outcomes and results of these papers are tabulated. We conclude that despite finding five clinical trials including one randomised controlled trial, that studied around 1400 patients who underwent LAA occlusion, the results of these studies do not clearly show a benefit for appendage occlusion. Indeed of the five studies, only one showed a statistical benefit for LAA occlusion, with three giving neutral results and in fact one demonstrating a significantly increased risk. One reason for this may be the inability to achieve acceptably high rates of successful occlusion on echocardiography when attempting to perform this procedure. The highest success rate was only 93% but most studies reported only a 55–66% successful occlusion rate when attempting closure in a variety of methods including stapling, ligation and amputation. Currently, the evidence is insufficient to support LAA occlusion and may indeed cause harm especially if incomplete exclusion occurs.

1. Introduction

A best evidence topic was constructed according to a structured protocol. This is fully described in the ICVTS [1].

2. Clinical scenario

You are performing a left atrial radiofrequency MAZE procedure on a patient who is also undergoing bypass grafting. It is your practice to also oversew the left atrial appendage (LAA) after this. While doing this, however, the thin left atrium tears and you spend the next 20 min repairing this tear with pledgets. As you comment to the anaesthetist that you wish that you had never tried to oversew the appendage, he also comments that on transoesophageal echocardiography (TOE) he often still sees quite a long residual stalk anyway and you both wonder if there really is an advantage to LAA removal.

3. Three-part question

In [patients undergoing cardiac surgery with atrial fibrillation] does [exclusion of the left atrial appendage] protect from [thromboembolic complications].

4. Search strategy

Medline 1950 to May 2009 using OVID interface

[exp Atrial Appendage/or left atrial appendage.mp OR (appendage.mp AND atr$.mp)] AND [excision.mp OR exclusion.mp OR ligation.mp OR occlusion.mp OR closure.mp OR obliteration.mp]

5. Search outcome

Three hundred and ten papers were found using the reported search from which 12 papers were identified that provided the best evidence to answer the question. These are presented in Table 1 .

Table 1

Best evidence papers

Author, date and country Patient group Outcomes Key results Comments 
Study type     
(level of evidence)     
Healey et al., (2005), This study included 77 Successful LAA 66% (44/52) This randomised controlled 
Am Heart J, Canada patients who were occlusion  trial is the first of its kind 
and Germany, [2] randomised in a ratio of 2:1   analysing LAA occlusion. 
 favouring left atrial Cardiopulmonary 72±27 min in the occlusion This study showed that 
Randomised occlusion during CABG bypass time group surgical occlusion can be 
controlled trial surgery. There were 52  75±39 min in the control successfully performed at 
(level Ia) patients who received LAA  group; P=0.63 CABG without increasing 
 occlusion and 25 patients   operation time, perioperative 
 who acted as controls Postoperative bleeding There were no increases in bleeding or heart failure. 
   perioperative bleeding Occlusion was successfully 
   (P=0.53), postoperative AF achieved in 2/3 of patients and 
   (P=0.56) or diuretic use improved with surgeon 
   (P=0.87) experience and use of stapling 
    device. There were two cases 
  Thromboembolic Two cases (2.6%) of thromboembolic events 
  events One intraoperatively and in the LAA occlusion group 
   one on day 3 compared to 11.6% of patients 
    who did not have LAA 
   No strokes were identified occlusion 
   postoperatively with a mean  
   follow-up of 13 months  
     
   Surveys sent to all eligible  
   patients revealed that 25  
   patients (11.6%) self reported  
   either a TIA or stroke with a  
   postoperative follow-up of  
   between 10 and 29 months  
     
Schneider et al., During a 12-month period, Successful LAA 17% (1/6) This is a small study which 
(2005), Cardiology, 6 female patients (age 61–81 closure  has shown that 83% of 
Germany, [3] years) with paroxysmal (3)   patients with LAA closure 
 or permanent (3) AF Thromboembolic One patient (17%) with were free from stroke at 
Case series underwent surgical LAA events permanent AF suffered a 15 months. With inadequate 
(level IV) closure at the time of mitral  stroke four weeks after closure occurring in 17% of 
 and/or aortic valve surgery  surgery patients, this study has 
    proposed that blood will 
  Left atrial thrombus Two patients (33%) showed become stagnant and increase 
   LAA thrombus which was the likelihood of the formation 
   absent in the preoperative of thrombus and thus stroke. 
   TEE This study therefore felt that 
    there is a need to improve the 
    surgical technique and verify 
    closure with echocardiographic 
    studies 
     
Bando et al., (2009) Between May 1977 and Thromboembolic Seventy-two patients had a Closure of the LAA failed to 
J Thorac Cardiovasc December 2001, 812 MVRs events late stroke; 47 (65%) of prevent late stroke 
Surg, Japan, [4] were performed. 493 (55%)  patients had the LAA closed  
 of patients had the LAA    
Retrospective closed; 320 patients Risk factor for late Closure of the LAA was not a  
cohort study undergoing MVR had stroke significant risk factor for  
(level IIb) concomitant ligation of the  late stroke (P=0.69)  
 LAA, whereas 173 patients    
 who underwent combined    
 MVR and the MAZE    
 procedure had the LAA    
 closed    
     
Kanderian et al., A total of 2546 patients Method of closure Fifty-two of 137 patients had When LAA is 
(2008), J Am Coll underwent closure of the  excision of the LAA (41 by performed, excision of 
Cardiol, USA, [5] LAA by various methods  scissors and 11 by a stapling the appendage using 
 for all types of cardiac  device), and 85 received scissors is the most 
Cohort study surgery between 1993 and  exclusion of the LAA of which reliable method. This 
(level IIIb) 2004. 137 patients were  73 of these (86%) were by study demonstrated a 
 included as follow-up data  suture and 12 (14%) by trend toward decreased 
 were available  stapler excision incidence of stroke/TIA 
    in patients with 
     
  Successful LAA closure Fifty-five of 137 patients successful LAA closure, 
   (40%) had successful LAA however, it was not 
   closure. LAA closure occurred statistically significant 
   more often with excision of the  
   LAA (73%) compared with  
   suture exclusion (23%) and  
   stapler exclusion (0%)  
   (P≤0.001)  
     
  Predictors of successful LAA excision was predictive  
  surgical outcome of successful procedural  
   outcome (P<0.001). Excluding  
   the LAA by either suture or  
   stapler techniques was more  
   likely to predict unsuccessful  
   LAA closure over scissors  
   (P≤0.001 and P=0.002,  
   respectively).  
     
  Thromboembolic Eighteen patients (13%)  
  events experienced stroke/TIA;  
   6 with LAA excision, 11 with  
   suture exclusion and 1 with  
   stapler exclusion. Of the 55  
   patients with successful LAA  
   closure, 6 (11%) had stroke/  
   TIA vs. 12 of 82 patients  
   (15%) with unsuccessful  
   LAA closure (P=0.61)  
     
García-Fernández This study consisted of 205 Successful closure of Complete ligation of the LAA This study shows that LAA 
et al., (2003), J Am patients who underwent LAA was achieved in 52 patients ligation during surgery for 
Coll Cardiol, Spain, MVR for rheumatic valve  (89.7%) MVR is consistent with a 
[6] disease In 170, endocarditis   reduction of the risk of late 
 in 10, severe ischaemic Thromboembolic Twenty-seven patients had embolism (6.7-fold reduction 
Cohort study regurgitation in 6 and mitral events an embolic event; 19 patients in embolic risk). If complete 
(level IIb) valve prolapse in 19  had an ischaemic stroke, five ligation is achieved and 
 patients  patients had a peripheral confirmed with TEE, a further 
   arterial embolism and 3 had a reduction in embolic risk is 
   TIA. Of the 27 patients with observed (11.9-fold) 
   an embolic event, two patients  
   had the LAA ligated  
     
   The occurrence of systemic  
   embolism was significantly  
   more frequent in patients  
   without LAA ligation  
   compared to patients with  
   LAA ligation (17% vs. 3.4%)  
   P=0.01  
     
   Multivariate analyses  
   identified the absence of LAA  
   ligation as an independent  
   predictor of the occurrence of  
   an embolic event after MVR  
   surgery [odds ratio 6.7 (95%  
   CI 1.5–31.0) P=0.02].  
   Moreover, if the absence of  
   effective ligation as assessed  
   by echocardiography was  
   included in the model, the odds  
   ratio increased up to 11.9  
   (95% CI 1.5–93.6) P=0.02  
     
Orszulak et al., All patients receiving a Risk of stroke There was a strong correlation This study found that ligation 
(1995), Eur J MVR (285) between  with late stroke in patients of the LAA during MVR+ 
Cardiothorac Surg, February 1979–December  who had the LAA ligated CABG was linked to an 
USA, [7] 1989 were studied. MVR was  when undergoing MVR increased risk of late stroke. 
     
 performed in isolation in  and CABG (P≤0.02), However, MVR alone did not 
Cohort study 199 and MVR with  however, correlation with increase the risk of late stroke 
(level IIb) concomitant CABG  isolated MVR cohort and the  
 was performed in 86  overall group did not reach  
 patients. Ninety-two  statistical significance  
 patients had operative  (P=0.81)  
 ligation of the LAA    
     
Johnsona et al., From 1995 to 1997, 437 Thromboembolic Twenty-one patients had a With no strokes related to the 
(2000), Eur J patients had the LAA events perioperative CVA of variable atrial appendage, this study 
Cardiothorac Surg, excluded during open-heart  severity with no evidence of has shown that removal of the 
USA, [8] operations  atrial clot on TOE. Seven appendage is safe and should 
   patients developed a CVA be considered 
Case study   postoperatively and 4 had  
(level IV)   AF, but again no atrial clots  
   were demonstrated  
     
Katz et al., (2000), Fifty patients undergoing Successful closure of 64% (32/50) Inadequate closure of the 
J Am Coll Cardiol, MVR and LAA ligation the LAA  LAA may act to increase the 
USA, [9] were studied   risk of thromboembolic events 
  Thromboembolic Four patients with an  
Case series  events incompletely ligated LAA had  
(level IV)   thromboembolic phenomena:  
   one stroke; one TIA; two  
   mesenteric emboli  
     
Almahameed et al., Between 1993 and 1998, Thromboembolic 14 (12.3%) Patients undergoing LAA 
(2007), J Cardiovasc 136 patients underwent events  exclusion during mitral valve 
Electr, USA, [10] LAA exclusion at the time   surgery have a significantly 
 of mitral valve surgery Warfarin status Seven of 67 (10%) patients increased risk of a 
Case study   prescribed warfarin had a thromboembolic event 
(level IV)   thromboembolic event especially when warfarin is 
   compared to 6 of 40 (15%) not prescribed upon 
   patients not prescribed hospital discharge 
   warfarin  
     
Fumoto et al., Fourteen mongrel dogs Successful closure 100% (14/14) In dogs, the third-generation 
(2008), J Thorac implanted with the third- of the LAA  atrial exclusion device achieved 
Cardiovasc Surg, generation atrial exclusion   easy, reliable and safe 
USA, [11] device at the base of the   exclusion of the LAA 
 LAA. The right atrial    
Case series appendage was stapled with    
(level IV) a commercial apparatus for    
 comparison    
     
Sick et al., (2007), All patients received the Successful LAA 54 of 58 patients (93%) had This study shows that LAA 
J Am Coll Cardiol, WATCHMAN LAA closure complete closure of the LAA occlusion with the 
USA, [12] occlusion device (75).   WATCHMAN device is 
 Sixty-six patients Thromboembolic No ischaemic strokes or safe and feasible with no 
Case study underwent successful device events systemic emboli occurred thromboembolic events in the 
(level IV) implantation   patients studied. 
     
Kamohara et al., Ten mongrel dogs had LAA Successful closure of 10/10 (100%) Device implantation is rapid, 
(2000), J Thorac occlusion device implanted LAA  reliable and a safe method of 
Cardiovasc Surg, into the LAA through a left   excision of the LAA 
[13] thoracotomy of their beating    
 heart    
Case series     
(level IV)     
Author, date and country Patient group Outcomes Key results Comments 
Study type     
(level of evidence)     
Healey et al., (2005), This study included 77 Successful LAA 66% (44/52) This randomised controlled 
Am Heart J, Canada patients who were occlusion  trial is the first of its kind 
and Germany, [2] randomised in a ratio of 2:1   analysing LAA occlusion. 
 favouring left atrial Cardiopulmonary 72±27 min in the occlusion This study showed that 
Randomised occlusion during CABG bypass time group surgical occlusion can be 
controlled trial surgery. There were 52  75±39 min in the control successfully performed at 
(level Ia) patients who received LAA  group; P=0.63 CABG without increasing 
 occlusion and 25 patients   operation time, perioperative 
 who acted as controls Postoperative bleeding There were no increases in bleeding or heart failure. 
   perioperative bleeding Occlusion was successfully 
   (P=0.53), postoperative AF achieved in 2/3 of patients and 
   (P=0.56) or diuretic use improved with surgeon 
   (P=0.87) experience and use of stapling 
    device. There were two cases 
  Thromboembolic Two cases (2.6%) of thromboembolic events 
  events One intraoperatively and in the LAA occlusion group 
   one on day 3 compared to 11.6% of patients 
    who did not have LAA 
   No strokes were identified occlusion 
   postoperatively with a mean  
   follow-up of 13 months  
     
   Surveys sent to all eligible  
   patients revealed that 25  
   patients (11.6%) self reported  
   either a TIA or stroke with a  
   postoperative follow-up of  
   between 10 and 29 months  
     
Schneider et al., During a 12-month period, Successful LAA 17% (1/6) This is a small study which 
(2005), Cardiology, 6 female patients (age 61–81 closure  has shown that 83% of 
Germany, [3] years) with paroxysmal (3)   patients with LAA closure 
 or permanent (3) AF Thromboembolic One patient (17%) with were free from stroke at 
Case series underwent surgical LAA events permanent AF suffered a 15 months. With inadequate 
(level IV) closure at the time of mitral  stroke four weeks after closure occurring in 17% of 
 and/or aortic valve surgery  surgery patients, this study has 
    proposed that blood will 
  Left atrial thrombus Two patients (33%) showed become stagnant and increase 
   LAA thrombus which was the likelihood of the formation 
   absent in the preoperative of thrombus and thus stroke. 
   TEE This study therefore felt that 
    there is a need to improve the 
    surgical technique and verify 
    closure with echocardiographic 
    studies 
     
Bando et al., (2009) Between May 1977 and Thromboembolic Seventy-two patients had a Closure of the LAA failed to 
J Thorac Cardiovasc December 2001, 812 MVRs events late stroke; 47 (65%) of prevent late stroke 
Surg, Japan, [4] were performed. 493 (55%)  patients had the LAA closed  
 of patients had the LAA    
Retrospective closed; 320 patients Risk factor for late Closure of the LAA was not a  
cohort study undergoing MVR had stroke significant risk factor for  
(level IIb) concomitant ligation of the  late stroke (P=0.69)  
 LAA, whereas 173 patients    
 who underwent combined    
 MVR and the MAZE    
 procedure had the LAA    
 closed    
     
Kanderian et al., A total of 2546 patients Method of closure Fifty-two of 137 patients had When LAA is 
(2008), J Am Coll underwent closure of the  excision of the LAA (41 by performed, excision of 
Cardiol, USA, [5] LAA by various methods  scissors and 11 by a stapling the appendage using 
 for all types of cardiac  device), and 85 received scissors is the most 
Cohort study surgery between 1993 and  exclusion of the LAA of which reliable method. This 
(level IIIb) 2004. 137 patients were  73 of these (86%) were by study demonstrated a 
 included as follow-up data  suture and 12 (14%) by trend toward decreased 
 were available  stapler excision incidence of stroke/TIA 
    in patients with 
     
  Successful LAA closure Fifty-five of 137 patients successful LAA closure, 
   (40%) had successful LAA however, it was not 
   closure. LAA closure occurred statistically significant 
   more often with excision of the  
   LAA (73%) compared with  
   suture exclusion (23%) and  
   stapler exclusion (0%)  
   (P≤0.001)  
     
  Predictors of successful LAA excision was predictive  
  surgical outcome of successful procedural  
   outcome (P<0.001). Excluding  
   the LAA by either suture or  
   stapler techniques was more  
   likely to predict unsuccessful  
   LAA closure over scissors  
   (P≤0.001 and P=0.002,  
   respectively).  
     
  Thromboembolic Eighteen patients (13%)  
  events experienced stroke/TIA;  
   6 with LAA excision, 11 with  
   suture exclusion and 1 with  
   stapler exclusion. Of the 55  
   patients with successful LAA  
   closure, 6 (11%) had stroke/  
   TIA vs. 12 of 82 patients  
   (15%) with unsuccessful  
   LAA closure (P=0.61)  
     
García-Fernández This study consisted of 205 Successful closure of Complete ligation of the LAA This study shows that LAA 
et al., (2003), J Am patients who underwent LAA was achieved in 52 patients ligation during surgery for 
Coll Cardiol, Spain, MVR for rheumatic valve  (89.7%) MVR is consistent with a 
[6] disease In 170, endocarditis   reduction of the risk of late 
 in 10, severe ischaemic Thromboembolic Twenty-seven patients had embolism (6.7-fold reduction 
Cohort study regurgitation in 6 and mitral events an embolic event; 19 patients in embolic risk). If complete 
(level IIb) valve prolapse in 19  had an ischaemic stroke, five ligation is achieved and 
 patients  patients had a peripheral confirmed with TEE, a further 
   arterial embolism and 3 had a reduction in embolic risk is 
   TIA. Of the 27 patients with observed (11.9-fold) 
   an embolic event, two patients  
   had the LAA ligated  
     
   The occurrence of systemic  
   embolism was significantly  
   more frequent in patients  
   without LAA ligation  
   compared to patients with  
   LAA ligation (17% vs. 3.4%)  
   P=0.01  
     
   Multivariate analyses  
   identified the absence of LAA  
   ligation as an independent  
   predictor of the occurrence of  
   an embolic event after MVR  
   surgery [odds ratio 6.7 (95%  
   CI 1.5–31.0) P=0.02].  
   Moreover, if the absence of  
   effective ligation as assessed  
   by echocardiography was  
   included in the model, the odds  
   ratio increased up to 11.9  
   (95% CI 1.5–93.6) P=0.02  
     
Orszulak et al., All patients receiving a Risk of stroke There was a strong correlation This study found that ligation 
(1995), Eur J MVR (285) between  with late stroke in patients of the LAA during MVR+ 
Cardiothorac Surg, February 1979–December  who had the LAA ligated CABG was linked to an 
USA, [7] 1989 were studied. MVR was  when undergoing MVR increased risk of late stroke. 
     
 performed in isolation in  and CABG (P≤0.02), However, MVR alone did not 
Cohort study 199 and MVR with  however, correlation with increase the risk of late stroke 
(level IIb) concomitant CABG  isolated MVR cohort and the  
 was performed in 86  overall group did not reach  
 patients. Ninety-two  statistical significance  
 patients had operative  (P=0.81)  
 ligation of the LAA    
     
Johnsona et al., From 1995 to 1997, 437 Thromboembolic Twenty-one patients had a With no strokes related to the 
(2000), Eur J patients had the LAA events perioperative CVA of variable atrial appendage, this study 
Cardiothorac Surg, excluded during open-heart  severity with no evidence of has shown that removal of the 
USA, [8] operations  atrial clot on TOE. Seven appendage is safe and should 
   patients developed a CVA be considered 
Case study   postoperatively and 4 had  
(level IV)   AF, but again no atrial clots  
   were demonstrated  
     
Katz et al., (2000), Fifty patients undergoing Successful closure of 64% (32/50) Inadequate closure of the 
J Am Coll Cardiol, MVR and LAA ligation the LAA  LAA may act to increase the 
USA, [9] were studied   risk of thromboembolic events 
  Thromboembolic Four patients with an  
Case series  events incompletely ligated LAA had  
(level IV)   thromboembolic phenomena:  
   one stroke; one TIA; two  
   mesenteric emboli  
     
Almahameed et al., Between 1993 and 1998, Thromboembolic 14 (12.3%) Patients undergoing LAA 
(2007), J Cardiovasc 136 patients underwent events  exclusion during mitral valve 
Electr, USA, [10] LAA exclusion at the time   surgery have a significantly 
 of mitral valve surgery Warfarin status Seven of 67 (10%) patients increased risk of a 
Case study   prescribed warfarin had a thromboembolic event 
(level IV)   thromboembolic event especially when warfarin is 
   compared to 6 of 40 (15%) not prescribed upon 
   patients not prescribed hospital discharge 
   warfarin  
     
Fumoto et al., Fourteen mongrel dogs Successful closure 100% (14/14) In dogs, the third-generation 
(2008), J Thorac implanted with the third- of the LAA  atrial exclusion device achieved 
Cardiovasc Surg, generation atrial exclusion   easy, reliable and safe 
USA, [11] device at the base of the   exclusion of the LAA 
 LAA. The right atrial    
Case series appendage was stapled with    
(level IV) a commercial apparatus for    
 comparison    
     
Sick et al., (2007), All patients received the Successful LAA 54 of 58 patients (93%) had This study shows that LAA 
J Am Coll Cardiol, WATCHMAN LAA closure complete closure of the LAA occlusion with the 
USA, [12] occlusion device (75).   WATCHMAN device is 
 Sixty-six patients Thromboembolic No ischaemic strokes or safe and feasible with no 
Case study underwent successful device events systemic emboli occurred thromboembolic events in the 
(level IV) implantation   patients studied. 
     
Kamohara et al., Ten mongrel dogs had LAA Successful closure of 10/10 (100%) Device implantation is rapid, 
(2000), J Thorac occlusion device implanted LAA  reliable and a safe method of 
Cardiovasc Surg, into the LAA through a left   excision of the LAA 
[13] thoracotomy of their beating    
 heart    
Case series     
(level IV)     

LAA, left atrial appendage; CABG, coronary artery bypass graft; AF, atrial fibrillation; MVR, mitral valve replacement; TIA, transient ischaemic attack; CI, confidence interval; CVA, cerebrovascular accident; TOE, transoesophageal echocardiography.

6. Results

There are two issues to address in this topic: is the LAA an important source of emboli in patients with AF and whether exclusion of the LAA reduces the incidence of thromboembolic events.

6.1. Left atrial appendage and source of emboli

Studies have concluded that approximately 90% of left atrial thrombi are located in the LAA [14, 15]. It follows that successful closure of the LAA should aid in reducing the risk of thromboembolic events in patients with AF [16]. Indeed, recurrent and persistent AF in patients who remain symptomatic with heart rate control and where anti-arrhythmic medication is not tolerated or no longer effective, then LAA ablation should be considered [17].

6.2. Exclusion of the LAA and thromboembolic events

Healey et al. [2] performed a randomised controlled clinical trial of 77 patients undergoing coronary artery bypass graft (CABG) surgery with 52 patients receiving LAA occlusion. Successful LAA occlusion was identified in only 66% of their study population, although this rate improved with experience.

Perioperative thromboembolic events were recorded for two patients; one an intraoperative ischaemic stroke and the other a transient ischaemic attack (TIA). No thromboembolic events were recorded during follow-up. Surveys were sent to all eligible patients for the study, but who chose not to participate and it showed that 12% self-reported a thromboembolic event (12 strokes and 13 TIAs).

During a 12-month period, Schneider et al. [3] examined six patients who received LAA closure at the time of mitral and/or aortic valve surgery. Postoperative TOE demonstrated successful closure in one patient. One patient experienced a stroke four weeks postoperatively despite a high level of anticoagulation.

Bando et al. [4] examined 812 patients following mitral surgery of whom 55% had their LAA ligated. Seventy-two patients experienced a late stroke. Of the 72 patients, 65% had the LAA ligated.

In 2008, Kanderian et al. [5] examined 137 patients who underwent LAA closure. They demonstrated that only 55% of their patients had successful closure of the LAA. They reported that 52 patients had excision of the LAA (41 by scissors and 11 by a stapling device) and 85 received exclusion of the appendage of which 73 were by suture and 12 by stapler excision. It was found that successful occlusion occurred more often with excision of the LAA (73%) relative to suture and stapler exclusion (23% and 0%, respectively). Six of 55 patients with successful closure experienced a stroke or TIA compared with 12 of 82 patients who had unsuccessful LAA closure, which was not significant.

García-Fernández et al. [6] examined 205 patients undergoing mitral valve surgery of which 58 patients received LAA ligation. Successful ligation was present in 89.7%. Twenty-seven patients, two of whom had their LAA ligated, experienced thromboembolic complications; 19 patients had an ischaemic stroke, five patients had a peripheral arterial embolism, and three patients experienced a TIA. Consequently, it was found that the occurrence of systemic emboli was more frequent among patients without relative to patients who had received LAA ligation. Moreover, this study demonstrated that the absence of ligation of the LAA was an independent predictor of the occurrence of an embolic event following mitral valve surgery with an odds ratio of 6.7. If the absence of effective ligation is incorporated into the model, the odds ratio increased to 11.9.

Orszulak et al. [7] examined 285 patients undergoing mitral valve replacement (MVR). Ninety-two patients received operative ligation of the LAA. This study found an increased rate of late stroke in patients who had the LAA ligated.

In 2000, Johnson et al. [8] studied 437 patients who received exclusion of the LAA during open heart surgery. Perioperative cerebrovascular accidents (CVAs) occurred in 21 patients despite no patients being identified by TOE to have intra-atrial clots. Seven patients developed a CVA postoperatively, four of whom were in AF, but no atrial clots were demonstrated on TOE.

Katz et al. [9] analysed 50 patients undergoing LAA ligation during MVR surgery. Incomplete ligation was detected in 36% of patients. Four patients with an incompletely ligated LAA had thromboembolic phenomena (one stroke; one TIA and two mesenteric emboli).

Almahameed et al. [10] studied 136 patients who underwent LAA ligation at the time of mitral valve surgery. Fourteen (12.3%) patients experienced thromboembolic events. They found a significantly increased rate of stroke in patients with LAA occlusion.

Fumoto et al. [11] studied 14 mongrel dogs implanted with the third-generation atrial exclusion device in their LAA. The right atrial appendage was stapled with commercial apparatus for comparison. LAA exclusion was complete and achieved without haemodynamic instability, and coronary angiography revealed that the left circumflex artery was patent in all cases.

Sick et al. [12] reported their experience with the WATCHMAN LAA occlusion device. The device was implanted into 75 patients, of whom 66 had successful implantation (88%). Complete closure of the LAA was observed in 93%. Three patients experienced device failure, two of which were embolisations and one was a delivery system failure due to a fractured wire.

Kamohara et al. [13] analysed ten mongrel dogs with the second generation atrial exclusion device implanted at the base of the LAA. This was performed without complication in all dogs.

7. Clinical bottom line

Despite finding five clinical trials including one randomised controlled trial that studied around 1400 patients who underwent LAA occlusion, the results of these studies do not clearly show a benefit for appendage occlusion. Indeed of the five studies, only one showed a statistical benefit for LAA occlusion, with three giving neutral results and in fact one demonstrating a significantly increased risk. One reason for this may be the inability to achieve acceptably high rates of successful occlusion on TOE when attempting to perform this procedure. The highest success rate was only 93% but most studies reported only a 55–66% successful occlusion rate when attempting closure in a variety of methods including stapling, ligation and amputation. Currently, the evidence is insufficient to support LAA occlusion and may indeed cause harm especially if incomplete exclusion occurs.

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