A long-term followup study on Boston Scientific’s (NYSE:BSX) Watchman heart implant shows low risk of hemorrhagic stroke and a high percentage of patients who discontinued anticoagulation drugs at one year.

Published this week in the Journal of the American College of Cardiology, the new registry data represent the largest number and longest follow-up of patients who have received a Watchman implant to-date. The left atrial appendage closure device (LAAC) is indicated for stroke prevention in patients with non-valvular atrial fibrillation (NVAF).

The article examines non-randomized, four-year data from the Continued Access to PROTECT AF (CAP) Registry and  five-year data from the Continued Access to PREVAIL (CAP2) Registry. Both registries had the same endpoints: primary efficacy of composite of stroke, systemic embolism, cardiovascular/unexplained death, and safety.

The findings include:

• The lowest rate of hemorrhagic stroke (CAP (0.17) and CAP2 (0.09) per 100 patient-years) recorded, despite more than 96% of the patients being considered at high risk of stroke.
• 94.3% procedural success rate in both CAP and CAP2, along with lower complications than other randomized clinical trials in this high-risk population.
• 95% of patients discontinued anticoagulation at one-year follow up.

CAP included 566 patients with an average follow-up of 50.1 months (2,293 patient-years), and CAP2 included
578 patients with an average follow-up of 50.3 months (2,227 patient-years). CAP2 patients were significantly older and had higher scores for congestive heart failure, hypertension, age of 65 to 75 years or older, diabetes, transient ischemic stroke, vascular disease, age and sex category — a composite known as CHA2DS2-VASc.

The primary composite endpoint occurred at a rate of 3.05 per 100 patient-years in CAP and 4.80 per 100 patient-years in CAP2, the article noted. Events contributing to this endpoint were most commonly cardiovascular/unexplained death (1.69 per 100 patient-years for CAP and 2.92 per 100 patient-years for CAP2).

Hemorrhagic stroke was significantly less than ischemic stroke (0.17 per 100 patient-years in CAP and 0.09 per 100 patient-years in CAP2), and total stroke rates were significantly less than predicted by the patient’s CHA2DS2-VASc scoreds— a 78% reduction with CAP, 69% reduction with CAP2.

“These registries, which contain the longest and largest follow-up data of patients with the Watchman device, support LAAC as a safe and effective therapy for long-term anticoagulation in patients with nonvalvular atrial fibrillation, and document the lowest rate of hemorrhagic stroke identified in this population,” the authors concluded.

Boston Scientific describes the Watchman as a permanent implant that is an alternative to the lifelong use of blood-thinners like warfarin for people with atrial fibrillation not caused by a heart valve problem. The Watchman was designed to reduce the risk of stroke without the danger of bleeding associated with blood-thinners, according to the company.

The Watchman has drawn scrutiny for its safety, efficacy and cost, and also for reporting on deaths associated with the device. More than 100,000 Watchman devices have been implanted worldwide, the company’s website notes.