Boston Scientific(BSX) WATCHMAN FLX, reduces bleeding risk by 45%... Anticoagulant alternative therapy ushers in a "turning point"

Boston Scientific (BSX) has confirmed that its cardiac surgery device ‘WATCHMAN FLX’ can achieve similar stroke prevention effects to blood thinners while significantly reducing the risk of bleeding. With the results of the global clinical trial ‘CHAMPION-AF’ published simultaneously in major conferences and medical journals, the possibility of a paradigm shift in the treatment of atrial fibrillation has been proposed.

On the 28th (local time), Boston Scientific announced that its WATCHMAN FLX left atrial appendage closure (LAAC) device met all primary safety and efficacy endpoints in a large-scale clinical trial involving patients with non-valvular atrial fibrillation (NVAF). The results were presented as a “landmark clinical trial” at the American College of Cardiology (ACC) Annual Scientific Session and were simultaneously published in the New England Journal of Medicine (NEJM).

Atrial fibrillation is a representative arrhythmia affecting approximately 59 million people globally, with a stroke risk up to five times that of normal sinus rhythm. It is reported that over 90% of thrombi in NVAF patients originate from the left atrial appendage. The current standard treatment is non-vitamin K oral anticoagulants (NOACs), while the WATCHMAN technology offers a permanent closure of this area through a single procedure, providing an alternative to long-term medication.

In a randomized controlled clinical trial involving 3,000 patients, the 36-month follow-up results showed that the WATCHMAN FLX had a statistically significant lower “bleeding risk” on the primary safety endpoint compared to NOACs. The rate of major and clinically relevant non-major bleeding that was unrelated to the procedure was 10.9%, a 45% reduction compared to the anticoagulant group (19.0%). Even in the analysis that included procedure-related bleeding, its incidence was 12.8%, which was still a 34% reduction compared to the control group.

Effectiveness was also shown to be non-inferior. On the primary efficacy endpoint that included stroke, cardiovascular death, unexplained death, and systemic embolism, the incidence of WATCHMAN FLX was 5.7%, meeting the “non-inferiority” criterion compared to NOACs (4.8%). Additionally, in a secondary assessment combining safety and efficacy, the device had an incidence of 15.1%, showing a “net clinical benefit” superior to anticoagulants (21.8%).

This CHAMPION-AF trial is the largest-scale LAAC clinical trial involving 141 institutions from the U.S., Canada, Europe, Japan, and Australia, with a procedural success rate of up to 99%. The study plans to continue follow-up observations for up to 5 years to gather more data.

Professor Martin Leon from Columbia University Medical Center commented, “This result is a ‘turning point’ in changing the drug-centered stroke prevention strategy,” adding, “It indicates the potential for WATCHMAN FLX to become a first-line treatment option in a broader patient population.”

Boston Scientific plans to leverage this data to advance the expansion of indications and insurance coverage. According to the company, approximately 40% of atrial fibrillation patients prescribed anticoagulants fail to adhere to the medication, increasing their stroke risk. Chief Medical Officer Brad Sutton stated, “WATCHMAN can provide lifelong protection through a single procedure,” and noted, “As clinical evidence accumulates, treatment options are expanding.”

The WATCHMAN device is a representative LAAC device that has been applied to over 600,000 patients to date, approved in Europe in 2009 and in the U.S. in 2015. Its latest model, WATCHMAN FLX Pro, received approval from the U.S. Food and Drug Administration (FDA) in 2023, with clinical trials underway to simplify post-operative antiplatelet therapy to a single drug.