To date, no study compared Amulet to the new Watchman FLX in terms of residual LAA patency or clinical outcomes in patients with percutaneous LAA closure. Patients undergoing LAA closure were randomly assigned (1:1) open-label to receive Amulet or Watchman 2.5 or FLX (Watchman) across 8 European centers in the investigator-initiated SWISS APERO trial (Comparison of Amulet Versus Watchman/FLX Device in Patients Undergoing Left Atrial Appendage Closure). At 45 days, the primary end outcome was a composite of justified crossover to a nonrandomized device during the LAA closure operation or residual LAA patency revealed by cardiac computed tomography angiography (CCTA). The secondary end goals were procedural complications, device-related thrombosis, per-device leak during transesophageal echocardiography, and clinical outcomes at 45 days.

 Between June 2018 and May 2021, 221 patients were randomly randomized to Amulet (111 [50.2%]) or Watchman (110 [49.8%]), with 25 (22.7%) patients receiving Watchman 2.5 before October 2019 and 85 (77.3%) receiving Watchman FLX. The primary end goal was assessed in 205 (92.8%) patients and occurred in 71 (67.6%) Amulet patients and 70 (70.0%) Watchman patients, respectively (risk ratio, 0.97 [95% CI, 0.80–1.16]; P=0.713). At 45-day CCTA, a single justifiable crossover occurred in an Amulet patient who met LAA patency requirements. Because of more frequent bleeding, major procedure-related problems occurred more frequently in the Amulet group (9.0% versus 2.7%; P=0.047) (7.2% versus 1.8% ). At 45 days, the per-device leak rate was higher with Watchman than with Amulet (27.5% versus 13.7%, P=0.020), though none were major (i.e., >5 mm). In contrast, device-related thrombus was detected in 1 (0.9%) patient with Amulet and 3 (3.0%) patients with Watchman at CCTA and in 2 (2.1%) & 5 (5.5%) patients at transesophageal echocardiography, Clinical results did not differ across groups after 45 days.

At 45-day CCTA, Amulet did not have a reduced rate of the composite of crossover or residual LAA patency compared to Watchman. In comparison to Watchman, Amulet was linked with reduced per-device leak rates at transesophageal echocardiography, increased procedural complications, and comparable clinical results at 45 days. Further research was needed to determine the clinical significance of CCTA-detected LAA patency.