Without Warfarin, Watchman Still Prevents Strokes, Says Registry

May 15, 2012

May 15, 2012 (Boston, Massachusetts) — The Watchman (Boston Scientific) left atrial appendage (LAA) closure device can do its job, cutting the risk of ischemic stroke in patients with atrial fibrillation (AF), entirely without oral anticoagulation, suggests a prospective registry of patients with warfarin contraindications [1].

That take from the observational ASA-Plavix (ASAP) Registry, presented here at the Heart Rhythm Society 2012 Scientific Sessions, adds to what had been observed in the Watchman's main randomized trial, Embolic Protection in Patients with Atrial Fibrillation (PROTECT-AF), in which patients with the device took warfarin for at least the first six weeks.

As covered extensively by heartwire , PROTECT-AF found the device noninferior to standard warfarin therapy for protection against stroke, cardiovascular death, or systemic embolism in patients with AF and a CHADS2 score >1.

Patients getting the Watchman in ASAP, who took clopidogrel for six months and aspirin indefinitely but without ever going on warfarin, still showed only a 1.7% rate of ischemic stroke--compared with 2.2% in the PROTECT-AF Watchman group, 7.3% in historical controls with ASAP-comparable CHADS2 scores taking aspirin alone, and 5.0% in such controls taking aspirin plus clopidogrel.

The findings, said Dr Vivek Y Reddy (Mount Sinai School of Medicine, New York, NY) when presenting the analysis, cast doubt on the need for even temporary warfarin in patients implanted with the Watchman.

Most strokes related to thrombus forming at the device would occur in the first six months after Watchman implantation, Reddy speculated; so if anything, eliminating the early warfarin might raise the stroke risk, not lower it. Given the low stroke rate seen in the ASAP registry, Reddy said, "it's not clear how important that 45 days of warfarin is. In fact, it's not clear that six months of [clopidogrel] helped at all."

The ASAP registry study included 150 patients at three centers in Germany and one in the Czech Republic who had nonvalvular AF and in terms of risk were similar to those included in PROTECT-AF, except they had contraindications to warfarin. Their mean CHADS2 score was 2.8. They received the Watchman and dual antiplatelet therapy for six months and aspirin thereafter and were followed for a mean of 14.4 months.

Measured as events per patient-year, the rate of death from any cause was 5.0%, of any stroke was 2.3%, and of ischemic stroke was 1.7%. The rate of major bleeding events, mostly gastrointestinal, was 2.7%

The Watchman is market-approved in Europe and was recommended for approval in the US by an FDA advisory committee, as reported by heartwire . But regulators declined to okay the device and asked for further trials. As a result, the Prospective Randomized Evaluation of the WATCHMAN LAA Closure Device in Patients With Atrial Fibrillation Versus Long Term Warfarin Therapy (PREVAIL) is currently recruiting, with a projected enrollment of 475 patients.

Reddy discloses receiving grant support from or consulting for Boston Scientific and receiving consulting fees or honoraria and research grants from AtriTech, which Boston Scientific purchased in 2011.Disclosures for the coauthors are listed in the abstract.

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