Prospective Randomized Evaluation of the Watchman Left Atrial Appendage Closure Device in Patients With Atrial Fibrillation Versus Long-Term Warfarin Therapy: The PREVAIL Trial

Study Questions:

How does left atrial appendage (LAA) occlusion compare with long-term oral anticoagulation in patients with nonvalvular atrial fibrillation (AF) who are at risk for thromboembolic events?


In the PREVAIL (Prospective Randomized Evaluation of the Watchman LAA Closure Device In Patients With Atrial Fibrillation Versus Long Term Warfarin Therapy)trial, patients with AF who had a CHADS2 score ≥2, or 1 and another risk factor, were randomized (in a 2:1 ratio) to the Watchman device or warfarin. Warfarin was discontinued in the device group after verification of optimal device positioning/function on transesophageal echocardiography performed 45 days after implantation, and continued in the medical group.


At 18 months, the composite rate of stroke, systemic embolism, and cardiovascular/unexplained death was 0.064 in the device group, and 0.063 in the control group, and did not achieve noninferiority. The rate of stroke or systemic embolism >7 days post-randomization was 0.0253 versus 0.0200, achieving noninferiority. The device was successfully deployed in 95% of patients (as compared with 91% in the earlier PROTECT AF study). Rate of complications (including cardiac perforation, tamponade, ischemic stroke, device embolization, and other vascular complications) occurring in the first 7 days after implant was 4.2% versus 8.7% in the earlier study.


The authors concluded that LAA occlusion with the Watchman device was not noninferior to warfarin with respect to the primary efficacy endpoint. The success and complication rates seem to have improved as compared to the earlier studies.


Although statistical criteria for noninferiority were not satisfied, the PREVAIL study confirms the efficacy and improved safety of the Watchman device. As the authors discuss, the failure to demonstrate noninferiority may have been due to the unexpectedly low event rates in the warfarin arm. The high success and relatively low complication rates were achieved despite enrolling higher-risk patients and the fact that nearly 40% of the procedures were performed by new operators. It is also noteworthy that the benefits of LAA occlusion are maintained, as evidenced by the lower mortality rate in the device group after long-term follow-up. LAA occlusion with the Watchman device is a reasonable alternative to long-term oral anticoagulation with warfarin. Whether LAA occlusion is superior or noninferior to long-term treatment with one of the novel oral anticoagulants is unknown.

Clinical Topics: Anticoagulation Management, Arrhythmias and Clinical EP, Noninvasive Imaging, Anticoagulation Management and Atrial Fibrillation, Atrial Fibrillation/Supraventricular Arrhythmias, Echocardiography/Ultrasound

Keywords: Stroke, Follow-Up Studies, Anticoagulants, Atrial Appendage, Patient Positioning, Warfarin, Atrial Fibrillation, Risk Factors, Embolism, Long-Term Care, Echocardiography, Transesophageal

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