Boston Scientific has shared a duo of positive data readouts from two separate trials evaluating its Watchman FLX left atrial appendage closure (LAAC) device in non-valvular atrial fibrillation (AF) patients, and its EKOS endovascular system in patients with intermediate-risk pulmonary embolism (PE).
The Watchman trial evaluated whether the device represented a reasonable alternative to non-vitamin K oral anticoagulants (NOACs) in patients with non-valvular AF, while the Ekos trial evaluated whether the endovascular system was superior to the current standard of care (SoC) – anticoagulation alone – in treating patients with acute PE.
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The results from each study were shared during the 2026 American College of Cardiology (ACC) conference, which took place from 28 to 30 March in New Orleans, Louisiana. The findings from each study were also simultaneously published in The New England Journal of Medicine.
In the 3,000-patient CHAMPION-AF (NCT04394546) trial, Watchman met its primary safety endpoint as a first-line option for stroke risk reduction in patients with non-valvular AF. The device proved statistically superior to NOACs at the three-year readout, achieving a 45% relative reduction in non-procedural bleeding risk.
The study’s primary efficacy endpoint, defined as the occurrence of stroke, cardiovascular or unexplained death or systemic embolism, was met, with Watchman achieving statistical non-inferiority compared to NOACs at 5.7% versus 4.8%.
Including procedural bleeding in a secondary analysis, Watchman was consistent with the primary safety endpoint and demonstrated a significant reduction in bleeding compared to NOACs, representing a 34% relative reduction in procedural and non-procedural bleeding risk.
“These positive data, which have the potential to support updated clinical guidelines globally, will be used in our submission to expand the indication and coverage for the well-established Watchman platform as a first-line stroke risk reduction option, providing physicians with more choices in care for a wider range of patients who have atrial fibrillation,” said Brad Sutton, chief medical officer, atrial fibrillation solutions at Boston Scientific.
“Today, 40% of patients with AF who are prescribed blood thinners for stroke risk reduction are not taking their medications consistently, significantly increasing their risk of stroke,” Sutton added.
Boston’s Watchman franchise represents a key revenue driver within the company’s cardiovascular portfolio. In Q4 2025, the franchise achieved a 29.4% uptick on its Q4 2024 performance, contributing $535m to Boston’s $3.4bn revenue performance in Q4 2025.
In the 544-patient HI-PEITHO trial (NCT04790370), Boston’s Ekos system’s delivery of a low dose of clot-dissolving medication directly to the blood clot to facilitate the dispersion of the medication deep into the clot to dissolve it was compared against the SoC of anticoagulation alone.
Meeting the trial’s co-primary endpoint of PE-related mortality, non-fatal hemodynamic cardiorespiratory decompensation or collapse and non-fatal symptomatic recurrence of PE within seven days, Ekos plus anticoagulation demonstrated superiority to anticoagulation alone at 4% versus 10.3%, representing a 61% reduction in the primary endpoint events. This result was achieved with no episodes of bleeding within the brain through 30 days.
Dr Michael Jaff, vice president and chief medical officer, vascular therapies at Boston Scientific, said: “The HI-PEITHO trial evaluated clear, clinically meaningful endpoints using rigorous patient enrolment criteria and demonstrated a definitive impact with the Ekos system over the standard of care for treating acute PE.
“For the first time, we have robust randomised clinical trial data available to inform treatment decisions by interventionalists and referring physicians and support consideration of Ekos plus anticoagulation as a first-line therapy.”
