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Left atrial appendage exclusion in patients with atrial fibrillation: Should it become standard of care?

Atrial fibrillation (AF) is the most common arrhythmia affecting the general population, with the prevalence projected to reach 12.1 million cases in 2030. It is well documented that AF is associated with a higher incidence of cardiovascular and cerebrovascular morbidity and mortality. In fact, AF is present in 25%–30% of patients who experience an acute ischemic stroke. Similarly, about one‐third of patients with AF will experience a stroke. Individuals of European descent have the highest lifetime risk of developing AF at 26% for men and 23% for women over the age of 40. Current management heavily relies on medical therapy in an effort to prevent these catastrophic complications. Unfortunately, no interventions have been proven to completely eliminate the adverse sequelae of this malignant process. In terms of medical treatments, several randomized and controlled studies, such as the AF‐CHF trial, have compared a rate‐control strategy with a rhythm‐control strategy in patients with AF. Overall, these studies have demonstrated a significantly lower rate of rehospitalization with a rate‐control strategy, but no significant differences in other major outcomes, such as all‐cause mortality, strokes, bleeding events, worsening heart failure, or quality of life. The ROCKET‐AF trial was aimed at comparing Warfarin to the novel factor Xa inhibitor Rivaroxaban, and it showed that there was no statistically significant difference between the two agents in terms of strokes or systemic emboli. However, it did reveal a statistically significant reduction in intracranial hemorrhages and fatal bleedings in the rivaroxaban compared with the Warfarin group. Since the mid‐1990s, attention has focused on the role of the left atrial appendage (LAA) and its association with the most feared complication of AF: thromboembolism. During normal sinus rhythm, the LAA contracts with the atrium and is thought to contribute to the “atrial kick,” which shortly precedes ventricular contraction. Patients with AF or other pathologies that lead to increased left ventricular end‐diastolic pressure can undergo remodeling of the left atrium, which leads to a static LAA and predisposes the patient to blood stasis and thrombus formation. A seminal review by Blackshear et al showed. that over 90% of left atrial thrombi in patients with nonrheumatic AF originated in the LAA. Common sense indicates that the LAA should be excluded in all patients with AF; however, procedures to exclude the LAA have yet to become the standard of care. Recent studies in the cardiac surgery literature, which are summarized inTable 1, indicate a clear benefit of LAA exclusion amongst patients with AF undergoing cardiac surgery. Interestingly, this benefit was found to extend well beyond the postoperative period, in cohorts that were equally anticoagulated and had similar CHA2DS2‐VASC scores. This observation from the LAAOS III trial indicated the long‐ term protective effect of a completely excluded LAA in this patient population. In fact, the benefit of LAA exclusion seemed to increase as time went on. This evidence further supports the facts that the LAA is a highly thrombogenic area even in patients without AF and that many patients may develop AF in the years after their cardiac surgeries. Having established that LAA exclusion is beneficial for patients with AF undergoing another cardiac surgery, what is the evidence supporting isolated LAA exclusion? Options for LAA exclusion that emerged over the years include endovascular options like the Watchman Device and surgical options like endocardial suture closure, stapler occlusion, and epicardial clip closure. Currently, the most used and studied approach for this procedure is the Watchman Device. This device is implanted percutaneously through the femoral vein, is safe in previous cardiac surgeries, and reduces systemic emboli in the long term. It is approved for patients who suffer from nonvalvular AF, but who have a contraindication to anticoagulation or some sensible reason not to want such therapy. However, some of the disadvantages of the Watchman Device are that it requires at least 6 weeks of Warfarin anticoagulation post procedure, and that it has a relatively high perioperative complication rate. The PREVAIL, PROTECT‐AF, and EWOLUTION trials, summarized in Table 2, all clearly show that while the Watchman is comparable or superior to Warfarin in terms of preventing systemic emboli and bleeding risk in the long term, it suffers from a perioperative complication rate of 2.8%–8.7%. A separate pitfall of the Watchman Device is that the first iterations of the device were not always suitable for every anatomic variation of the LAAs. This is an issue that has been somewhat ameliorated in the more recent generations of the device. An interesting alternative to the Watchman Device that has emerged is LAA clipping. This is a procedure that can be done in a minimally invasive thoracoscopic fashion, often as same‐day surgery. van Laar et al. studied this procedure in 222 subjects with an average CHA2DS2‐VASc score of 2.3 and reported 0 TIA, strokes or systemic emboli at 30 days post op. They observed cerebrovascular event rate as low as 0.5 per 100 patient‐years, with 57% of patients not receiving oral anticoagulation therapy at the latest follow‐up of 20 months. Similarly, in a study of 45 by Branzoli et al., where the average CHA2DS2‐VASc was 6.5, it was found that none of the subjects suffered any complications at 16 months without complications after atrial appendage clipping. Finally, Cartledge et al., in