CHAMPION-AF study of the WATCHMAN FLX™ Left Atrial Appendage Closure Device as a first-line therapy for stroke risk reduction meets all primary and secondary safety and efficacy endpoints

MARLBOROUGH, Mass. and NEW ORLEANS, March 28, 2026 /PRNewswire/ -- Boston Scientific Corporation (NYSE: BSX) today announced that the CHAMPION-AF global clinical trial met all primary and secondary safety and efficacy endpoints. The study evaluated the WATCHMAN FLX™ Left Atrial Appendage Closure (LAAC) Device compared to non-vitamin K antagonist oral anticoagulants (NOACs) as a first-line option for stroke risk reduction in a broad population of patients with non-valvular atrial fibrillation (NVAF). Key results were presented as a late-breaking clinical trial at the American College of Cardiology's Annual Scientific Session & Expo and simultaneously published in The New England Journal of Medicine.

Atrial fibrillation (AF) is an increasingly common heart rhythm disorder that affects approximately 59 million people worldwide¹ and increases stroke risk by five times compared to people with a normal heart rhythm.² In patients with NVAF, more than 90% of heart-related blood clots form in the left atrial appendage (LAA).³ An alternative to long-term NOACs – considered the leading contemporary blood thinners for stroke risk reduction in patients with NVAF – the WATCHMAN technology is designed to permanently close off the LAA and is implanted in a single procedure.

"The success of the landmark CHAMPION-AF trial represents a meaningful milestone that will undoubtedly transform the treatment approach to stroke risk reduction in a broader population of patients who historically have needed to rely on medication," said Martin Leon, M.D., study co-chair and Mallah Family professor of cardiology, chief innovation officer and director, Cardiovascular Data Science Center, Columbia University Medical Center.* "These results should give clinicians confidence in the potential of the WATCHMAN FLX device to become a first-line treatment option for reducing the risk of stroke for a rapidly growing number of patients with AF."

The randomized, controlled trial enrolled 3,000 patients with NVAF who were suitable for oral anticoagulation therapy across a broad spectrum of stroke and bleeding risk. At 36 months:

• The primary safety endpoint was met with data demonstrating the WATCHMAN FLX device was statistically superior to NOACs (10.9% vs. 19.0%; P<0.001) for non-procedural major and clinically relevant non-major bleeding, achieving a 45% relative reduction in non-procedural bleeding risk.
  • When including procedural bleeding in a secondary analysis, the WATCHMAN FLX device performance was consistent with the primary safety endpoint, demonstrating a significant reduction in bleeding compared to NOACs (12.8% vs. 19.0%; P<0.001) for major and clinically relevant non-major bleeding, representing a 34% relative reduction in procedural and non-procedural bleeding risk.
• The primary efficacy endpoint, defined as occurrence of stroke, cardiovascular or unexplained death or systemic embolism, was met with the WATCHMAN FLX device achieving statistical non-inferiority compared to NOACs (5.7% vs. 4.8%; P<0.001).

The study's secondary safety endpoint underscored the WATCHMAN FLX device is statistically non-inferior to NOACs at 36 months for procedural and non-procedural major bleeding (5.9% vs. 6.4%; P<0.001). Additionally, a secondary combined safety and efficacy endpoint highlighted a net clinical benefit with the device demonstrating statistical superiority to NOACs for the occurrence of cardiovascular death, stroke, systemic embolism and non-procedural major bleeding and clinically relevant non-major bleeding (15.1% vs. 21.8%; P<0.001).  

CHAMPION-AF is the largest clinical trial comparing an LAAC device to NOACs for patients with NVAF to date and included 141 sites in the U.S., Canada, Europe, Japan and Australia, which implanted the devices with a 99% procedural success rate. Patient follow-up in the CHAMPION-AF trial will continue through five years and will include additional primary and secondary endpoints.

"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, M.D., chief medical officer, Atrial Fibrillation Solutions, 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.⁴ The CHAMPION-AF data add to Boston Scientific's robust body of clinical evidence supporting the WATCHMAN device as a one-time implant that helps provide stroke risk protection over a patient's lifetime."

More than 600,000 people have been treated with the WATCHMAN implant, which is the most implanted and studied LAAC device on the market. The WATCHMAN LAAC device was first introduced to the European market in 2009 and was approved by the U.S. Food and Drug Administration (FDA) in 2015. The latest-generation WATCHMAN FLX™ Pro LAAC Device was approved in the U.S. in 2023 and is currently being studied in several clinical trials, including the SIMPLAAFY randomized controlled trial, which is evaluating single-drug alternatives to dual anti-platelet therapy as a post-procedural regimen.

For more information about the CHAMPION-AF trial, visit watchman.com/CHAMPION

About Boston Scientific

Boston Scientific transforms lives through innovative medical technologies that improve the health of patients around the world. As a global medical technology leader for more than 45 years, we advance science for life by providing a broad range of high-performance solutions that address unmet patient needs and reduce the cost of healthcare. Our portfolio of devices and therapies helps physicians diagnose and treat complex cardiovascular, respiratory, digestive, oncological, neurological and urological diseases and conditions. Learn more at www.bostonscientific.com and follow us on LinkedIn.  

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