Boston Scientific spotlights real-world safety data from its Watchman FLX heart plug implant

After the FDA said last year it would keep a closer eye on the potential complications of a type of permanent heart plug designed to cut the risk of stroke, Boston Scientific has put forward real-world safety data gathered on its left atrial appendage occlusion device, the Watchman.

The minimally invasive implant is snaked into the heart via a catheter and is used to help seal up a small pocket in the cardiac muscle wall. Among people with atrial fibrillation, an irregular heartbeat can cause blood to pool in this pocket, which can lead to the formation of clots that could potentially become lodged in the brain or elsewhere.

Last September, the agency took steps to alert healthcare providers of potential risks of the procedure itself after a study of nearly 50,000 patients showed major side effects were more common in women than in men. The root cause of the difference has not yet been determined, and the FDA said it believes the implants’ benefits continue to outweigh the risks.

Last year also saw the introduction of a new U.S. competitor to Boston Scientific’s Watchman and its upgraded Watchman FLX model: Abbott’s Amplatzer Amulet, which received approval in August 2021. Appendage closures can also be performed during open surgery with sutures or staples while surgeons are operating on a separate heart condition.

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The latest data from Boston Scientific spanned more than 16,000 patients with atrial fibrillation that was not caused by issues with a heart valve and who received the newer Watchman FLX. 

Researchers found major complications occurred in 0.37% of cases during the week after the procedure or after discharge from the hospital. This included cases of death, ischemic stroke, systemic embolism or device-related side effects that required open surgery or major endovascular intervention.

At the 45-day mark, the registry had logged a 0.51% rate of pericardial effusion—or the dangerous buildup of fluids around the heart requiring either surgical or needle-based interventions to drain them—while only 0.03% of patients needed cardiac surgery. Implantations were successfully performed in 97.6% of patients, the company said in a statement.

The findings were presented during a late-breaking trial session at the Cardiovascular Research Technologies annual meeting, and the study will continue to track patients for at least two years after receiving the implant. 

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Last year’s analysis, published in JAMA Cardiology, only collected data on the first-generation Watchman device. It found that in-hospital cases of major bleeding occurred in 1.7% of women compared to 0.8% in men, while rates of pericardial effusion were logged at 1.2% versus 0.5%.

At the time, the FDA said in a letter to healthcare providers that it would “work with the manufacturers of approved LAAO devices to evaluate information from several sources including premarket studies, mandated postmarket studies and real-world data to provide additional information on this issue.” 

Last summer also saw late-breaking clinical trial data comparing the Watchman to Abbott’s Amplatzer Amulet, which has been available in Europe since 2013. They showed that among more than 1,800 patients with an average age of 75, the Amulet was correctly placed in 98.4% of procedures compared to 96.4% with the Watchman device, leading to appendage closures in 98.9% of cases compared to 96.8%, respectively.

While Boston Scientific’s version opens more like an umbrella to help fill the pouch, Abbott’s flattens into a mesh disc to block off the opening while expanding a separate shape to fill the inside of the appendage. Compared to the original Watchman, the next-generation Watchman FLX is available in more sizes to help fit smaller and larger openings or shallower appendages than its predecessor. The FLX, approved in July 2020, can also be fully recaptured, repositioned and redeployed during a procedure.