AMPLATZER™ AMULET™ LEFT ATRIAL APPENDAGE OCCLUDER VERSUS WATCHMAN™ DEVICE FOR STROKE PROPHYLAXIS (AMULET IDE): A RANDOMIZED CONTROLLED TRIAL.

Background: Percutaneous closure of the left atrial appendage (LAA) is an alternative to chronic oral anticoagulation to reduce stroke risk in patients with non-valvular atrial fibrillation (NVAF). The Amplatzer™ Amulet™ LAA Occluder IDE Trial (Amulet IDE Trial) was designed to evaluate the safety and effectiveness of the dual-seal mechanism of the Amulet LAA occluder compared with the Watchman™ device. Methods: Patients with NVAF at increased risk of stroke were randomly assigned (1:1) to undergo percutaneous implantation of a LAA occluder with the Amulet occluder or Watchman device. The primary endpoints included safety (composite of procedure-related complications, all-cause death, or major bleeding at 12 months) and effectiveness (composite of ischemic stroke or systemic embolism at 18 months) and the rate of LAA occlusion at 45 days. Pre-specified secondary endpoints included a composite of all stroke, systemic embolism, or cardiovascular/unexplained death at 18 months, major bleeding at 18 months, and superiority test of the three primary endpoints. Results: A total of 1878 patients were enrolled. The Amulet occluder was noninferior to the Watchman device for the primary safety endpoint (14.5% vs. 14.7%; difference=-0.14, 95% CI, -3.42-3.13; p<0.001 for noninferiority). Major bleeding and all-cause death were similar between groups (10.6% vs 10.0% and 3.9% vs 5.1%, respectively). Procedure-related complications were higher for the Amulet occluder (4.5% vs. 2.5%), largely related to more frequent pericardial effusion and device embolization. The Amulet occluder was noninferior to the Watchman device for the primary effectiveness endpoint (2.8% vs. 2.8%; difference=0.00, 95% CI, -1.55-1.55; p<0.001 for non-inferiority), and the composite of stroke, systemic embolism or cardiovascular/unexplained death (5.6% vs 7.7%, difference=-2.12, 95% CI, -4.45-0.21; p<0.001 for noninferiority). The rate of major bleeding was similar between groups (11.6% vs. 12.3%; difference=-0.71, 95% CI -3.72-2.31; p=0.32 for superiority). LAA occlusion was higher for the Amulet occluder compared with the Watchman device (98.9% vs. 96.8%; difference=2.03, 95% confidence interval [CI], 0.41-3.66; p<0.001 for noninferiority; p=0.003 for superiority). Conclusions: The Amulet occluder was non-inferior for safety and effectiveness of stroke prevention for NVAF compared with the Watchman device, and superior for LAA occlusion. Procedure-related complications were higher with the Amulet device and decreased with operator experience. Clinical Trial Registration: URL https://clinicaltrials.gov Unique Identifier NCT02879448.