Boston Sci's Watchman Takes Heat

U.S. FDA and CMS approvals were based on incomplete information, according to a prominent cardiologist.

Nancy Crotti

A prominent cardiologist is calling for colleagues to stop using Boston Scientific's Watchman device, which is meant to prevent strokes in patients with atrial fibrillation.

John Mandrola, MD, a cardiac electrophysiologist practicing in Louisville, KY, writes in his regular Medscape.com column that the Watchman left atrial appendage closure device does not prevent stroke any better than anticoagulation drug warfarin. The device is designed to stop blood clots in the heart from reaching the brain.

Mandrola writes that he's feeling pressure from colleagues to use the device, and that other hospitals in Louisville are performing and promoting the procedure. He also cites "irrational exuberance for this procedure," including at the recent Transcatheter Cardiovascular Therapeutics 2016 conference "at which a deeply flawed study was touted."

Boston Scientific defended its device. "Boston Scientific stands behind the robust body of evidence supporting the Watchman implant which led to FDA approval and the subsequent CMS national coverage decision for the therapy in the U.S., as well as approval and licensing in 75 countries," company spokesperson Trish Backes wrote in an email statement.

Mandrola points to results of the Prevail trial, which was published in 2014 and compared Watchman and warfarin in 407 high-risk patients with AF (mean CHA2DS2-VASc=3.8). Researchers studied safety, primary efficacy, and late ischemic efficacy end points, the latter of which excluded events that occurred in the first week after the implant. The late ischemic end point was added to show proof-of-concept that LAA occlusion prevented events.

In 269 patients who had the Watchman implanted, there were six ischemic strokes or systemic embolism, compared with one such event in the control arm's 138 patients, Mandrola noted. The results, published in the Journal of the American College of Cardiology, showed Watchman achieved non-inferiority to standard treatment in the 28% of patients who reached the 18-month follow-up period.

But at TCT in September of that year and in an October 2014 FDA hearing on the device, study co-author Vivek Reddy, MD, presented longer-term data from Prevail that included eight new ischemic strokes in the Watchman arm, for a total of 13, versus one in the control group.

FDA approved the Watchman in 2015, followed by a CMS decision that proposed guidelines that November saying that "the evidence is sufficient to determine percutaneous left atrial appendage closure therapy using an implanted device is not reasonable and necessary to diagnose or treat an illness or injury or to improve the functioning of a malformed body member," making it ineligible for broad reimbursement.

Instead, CMS proposed seven conditions for coverage, including participation in a national registry that would follow patient outcomes for five years after implantation. Then, in February 2016, CMS approved the Watchman for national coverage under specific criteria, including that the patient is unable to take the long-term oral anticoagulant that CMS considers to be the first line of therapy against stroke risk. It removed the requirement for clinical trial participation.

Mandrola wrote in December 2015 that he believed CMS's more cautious approach was correct.

"The evidence is clear and consistent: occlusion of the left atrial appendage with Watchman fails to protect against ischemic events," Mandrola writes. "I'm not a statistician, but updated results of a trial, results that include more patients reaching longer-term follow-up, increases our knowledge about device efficacy. These data show Watchman as inferior to warfarin, yet influential leaders in the field keep citing the incomplete Prevail paper."   

In a handful of comments to the Medscape article, two writers likened the Watchman situation to the Hans Christian Andersen tale, "The Emperor's New Clothes." 

Nancy Crotti is a contributor to Qmed.

Like what you're reading? Subscribe to our daily e-newsletter.

[Watchman image courtesy of Boston Scientific]