SIMPLAAFY Results Presented for Antithrombotic Strategies After LAAC With Boston Scientific’s Watchman FLX Pro

November 3, 2026—Six-month results from the randomized SIMPLAAFY trial comparing three antithrombotic strategies after left atrial appendage closure (LAAC) with Boston Scientific’s Watchman FLX Pro device were presented at TCT 2026 and simultaneously published by Vivek Y. Reddy, MD, et al in Journal of the American Association. Aspirin alone and a reduced-dose non–vitamin K antagonist oral anticoagulant (NOAC) strategy each met noninferiority compared with dual antiplatelet therapy (DAPT) for the primary composite endpoint.

The prospective, multicenter, randomized controlled trial enrolled selected patients with nonvalvular atrial fibrillation who were considered eligible for monotherapy after LAAC. Following successful device implantation, 1,857 patients were randomized to aspirin monotherapy throughout the trial (n = 613), reduced-dose NOAC for 3 months followed by aspirin (n = 620), or DAPT for 6 months followed by aspirin monotherapy (n = 624).

According to the CRF press release, the primary endpoint (a composite of all-cause death, stroke, systemic embolism, or major bleeding at 6 months) occurred in 3.3% of patients assigned to aspirin alone, 5.1% assigned to reduced-dose NOAC, and 6.9% assigned to DAPT. The absolute differences compared with DAPT were 3.6 percentage points for aspirin and 1.8 percentage points for reduced-dose NOAC. Both strategies met the criterion for noninferiority (P < .0001 for each comparison).

Ischemic stroke occurred in 0.7% of patients in each group through 6 months. Clinically relevant bleeding rates were 3.8% with aspirin alone, 4.8% with reduced-dose NOAC, and 8.7% with DAPT.

At 45-day imaging, device-related thrombus was observed in 0.9% of patients in the reduced-dose NOAC group compared with 2.7% in the aspirin group and 3.4% in the DAPT group.

“These findings suggest that, after uncomplicated LAAC, antithrombotic therapy may be simplified to aspirin alone or a reduced-dose NOAC, with treatment tailored to each patient’s bleeding risk, risk of device-related thrombosis and personal preferences,” commented study Co-Chair Saibal Kar, MD, in the press release. “The prespecified 12-month analysis will also provide further insight into longer-term efficacy.”

Dr. Kar is Program Director of the cardiovascular disease fellowship at Los Robles Health System and National Physician Director of Interventional Cardiology at HCA Healthcare.