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New catheter based strategies like mechanical occlusion of the Left Atrial Appendage (LAA) with a Watchman device or ligation of the LAA (LARIAT procedure) have been developed in the recent past for prevention of stroke in patients with atrial fibrillation (AF). In the PROTECT-AF study, LAA occlusion was shown to be non-inferior to warfarin for the prevention of the primary composite endpoint of stroke, death and systemic embolism. Another study , the PREVAIL trial(1), was recently conducted to address the concerns regarding the trial design, definition of endpoints and the higher incidence of peri-procedural adverse events in the PROTECT-AF study. The PREVAIL study, when compared with the PROTECT-AF study, included a higher risk group i.e., the patients were older (74.0 ± 7.4 years vs. 71.7 ± 8.8 years) and had higher CHADS2 scores (2.6 ± 1.0 vs. 2.2 ± 1.2).
The study enrolled 407 patients; 269 were randomized to the device group in whom watchman device was implanted and 138 to the control group who received warfarin during the study with a mean follow up of 11.8± 5.8 months. First primary efficacy end-point was a composite of stroke & systemic embolism and cardiovascular/unexplained death. The mean 18-month event rate ratio of the primary efficacy endpoint was 1.07 (95% credible interval (CI): 0.57 to 1.89, 0.064 device vs 0.063 control). As the upper boundary of 1.89 was not lower than the pre-specified non-inferiority margin of 1.75, statistical non-inferiority was not achieved. This was attributed to substantially lower-than-expected number of events, particularly in the control group. Second primary efficacy endpoint, which is the rate of stroke or SE > 7days after randomization was 0.0253 for the device group and 0.0200 for the control group (18-month risk difference 0.0053 [ 95% CrI: -0.0190 to 0.0273]). Because the 95% upper CrI of risk difference was <0.0275 (which was the rate difference non-inferiority criterion), the Watchman device was considered non-inferior to warfarin for prevention of second primary efficacy endpoint.
Procedural success, defined as device deployment and release increased from 90.9% in PROTECT AF to 95.1% in PREVAIL. Procedural complications within 7 days of the procedure decreased from 8.7% in PROTECT AF to 4.2% in the PREVAIL.
Conclusion: This multicenter randomized study showed: 1) Combined efficacy endpoint of early and late events was similar with Watchman device but did not meet the criteria of non-inferiority. 2) LAA occlusion with Watchman device was non-inferior to chronic warfarin for the prevention of stroke and SE beginning 1 week after randomization. 3) Procedural complications occurring after LAA occlusion were infrequent and decreased significantly when compared to PROTECT AF trial.
1. Holmes DR, Jr., Kar S, Price MJ et al. Prospective randomized evaluation of the Watchman Left Atrial Appendage Closure device in patients with atrial fibrillation versus long-term warfarin therapy: the PREVAIL trial. Journal of the American College of Cardiology 2014;64:1-12.
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