Should patients undergoing cardiac surgery with atrial fibrillation have left atrial appendage exclusion?

Summary

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 .

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.

References