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Study Summary

The LAAOS III trial was designed to test whether or not surgical left atrial appendage (LAA) occlusion would lead to a reduction in ischemic stroke or systemic embolism in patients with atrial fibrillation undergoing cardiac surgery. A total of 4,770 patients underwent randomization: 2,379 assigned to LAA occlusion at time of surgery, and 2,391 assigned to anticoagulation alone. Pursed-string suturing of the LAA and percutaneous devices were not allowed. Mean CHA2DS2-VASc score was 4.2 in each arm. At a mean follow-up of 3.8 years, the incidence of ischemic stroke or systemic embolism was 4.8% in the LAA occlusion group and 7.0% in the anticoagulation only group (HR 0.67, 95% CI: 0.53-0.85; P = 0.001; see accompanying Hurst’s Central Illustration). Anticoagulation usage at 1-year follow-up was 79.6% and 78.9% in the occlusion and no-occlusion groups, respectively, with about 50% of patients on non-vitamin K oral anticoagulants and 50% on vitamin K antagonists at 3 years. Bleeding did not differ significantly between the two groups. In addition, there were no significant differences in hospitalization for heart failure, myocardial infarction, or death between the two groups.


Study Strengths: LAAOS III is the first randomized, controlled trial to demonstrate significant reduction in cardioembolic events with surgical LAA closure in patients with atrial fibrillation while undergoing cardiac surgery as compared to patients who did not undergo LAA closure. Importantly, both groups in this trial had a high usage of anticoagulation after cardiac surgery (75.3% and 78.2% in LAA occlusion and no-occlusion groups, respectively, at 3 years). Therefore, this study suggests surgical LAA occlusion has an additive effect to anticoagulation in prevention of cardioembolic events.

Study Limitations: LAAOS III did not compare surgical LAA occlusion with anticoagulation, and therefore one cannot conclude based on the results of this trial that anticoagulation can be discontinued in patients with surgical LAA closure. LAAOS III also did not allow for percutaneous LAA occlusion devices to be used in this study and therefore we cannot extrapolate the results of this trial to such devices. Last, but not least, the surgical occlusion techniques were specifically limited to amputation and closure, stapler closure, double-layer linear closure from within the atrium (in patients undergoing minithoracotomy), or closure with an epicardial occlusion device in this trial; therefore, purse string sutures should not yet be considered a viable technique for surgical LAA occlusion.

Next Steps/Clinical Perspective: LAAOS III showed that surgical LAA occlusion in addition to baseline anticoagulation therapy leads to a significant reduction in cardioembolic events compared to anticoagulation alone. Anticoagulation has been shown to have a robust benefit in preventing cardioembolic events in patients at high risk of stroke. However, anticoagulation is limited by problems that include incorrect dosing, temporary interruptions, patient non-adherence, and for vitamin K antagonists, poorly controlled INRs. Surgical occlusion likely reduces the risk of a cardioembolic event by a different means and is additive to the effect of anticoagulation. The next steps include testing surgical LAA occlusion without anticoagulation against anticoagulation, but this would require another trial.

Trial Reference

Whitlock  RP, Belley-Cote  EP, Paparella  D,  et al. Left atrial appendage occlusion during cardiac surgery to prevent stroke. N Engl J Med. doi: 10.1056/NEJMoa2101897

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