Boston Scientific has announced positive six-month primary endpoint results from the SIMPLAAFY randomised controlled trial of the Watchman FLX Pro left atrial appendage closure (LAAC) device.
The study evaluated two single-drug regimens as alternatives to dual antiplatelet therapy (DAPT) following implantation of the device in patients with non-valvular atrial fibrillation (AF).
Key results were presented as a late-breaking clinical trial at the 2026 Transcatheter Cardiovascular Therapeutics (TCT) conference (31 October–3 November, San Diego, USA) and simultaneously published in the Journal of the American Medical Association (JAMA).
The trial sought to determine if either reduced-dose non-vitamin K oral anticoagulants (NOACs) or aspirin alone are non-inferior to DAPT for the composite clinical endpoint of death, stroke, systemic embolism, or major bleeding, through six months post LAAC.
“For patients with non-valvular AF who undergo an LAAC procedure, balancing short-term bleeding risk with the need to maintain stroke protection during post-procedure healing is critical,” said study co-chair Saibal Kar (Los Robles Regional Medical Center, Thousand Oaks, USA). “The findings from the SIMPLAAFY trial are encouraging, and highlight the potential to meaningfully simplify post-procedure care and reduce medication burden for patients following Watchman FLX Pro implantation.”
The study randomised 1,857 patients across 86 clinical study sites in the USA to a post-implant regimen of aspirin alone for the duration of the trial or reduced-dose NOACs for the first three months followed by aspirin only or a DAPT regimen of aspirin and clopidogrel antiplatelet medication for the first six months, followed by aspirin only.
At six months, data demonstrated that the aspirin alone and reduced-dose NOAC alone regimens each achieved non-inferiority to DAPT, with patients on these regimens experiencing less bleeding and equivalent ischaemic stroke rates to DAPT (0.7%). Additionally, imaging at 45 days also showed the rate of device-related thrombus, or clotting, was lowest in the patients on a reduced-dose NOAC compared to DAPT (0.9% vs. 3.4%).
