HRS: Watchman still strong for stroke prevention, even without warfarin
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BOSTON—Implantation of the Watchman device (Boston Scientific) without a warfarin transition is safe and effective in atrial fibrillation (AF) patients with contraindications to even short-term oral anticoagulation, according to an analysis of the ASA Plavix registry, presented May 11 as a late-breaking clinical trial at the 33rd annual scientific sessions of the Heart Rhythm Society.

AF patients at the highest risk for embolic stroke also experience the greatest risk of hemorrhagic complications of anticoagulant use. The researchers noted that the PROTECT AF trial revealed that left atrial appendage (LAA) closure using the Watchman device was non-inferior to warfarin for preventing stroke in AF patients with CHADS2. However, these patients were treated with warfarin post-implant until a transesophageal echocardiography (TEE) demonstrated LAA closure at six weeks.

Due to the “pressing need” for strategies that can prevent stroke in patients with contraindications to warfarin, the researchers said they designed and conducted this prospective study of Watchman implantation in warfarin-contraindicated patients.

Vivek Y. Reddy, MD, director of cardiac arrhythmia service at Mount Sinai Medical Center in New York City, and colleagues enrolled 150 patients at four centers. The mean age was 72.5 years.

The patients had nonvalvular AF, a CHADS2 score of at least 1 and a contraindication to warfarin use. Post-implant, patients were discharged on six months of clopidogrel and life-long aspirin. Follow-up TEE was performed at three months and 12 months.

In terms of patient characteristics, the prevalence of stroke risk factors were: 29 percent of patients had congestive heart failure; 95 percent had hypertension; 43 percent were 75 years or older; 32 percent had diabetes mellitus; and 41 percent had a prior stroke or transient ischemic attack. The mean CHADS2 score was 2.8.

In this population, the reason for warfarin contraindication was: hemorrhagic tendencies (26 percent), blood dyscrasias (7 percent), bleeding tendencies (67 percent), unsupervised patients with senility/high fall risk (4 percent) and other (5 percent).

Watchman implantation was successful in 94 percent of the cases. With a mean follow-up of 14.2 months, and 93 patients followed for at least one year, there were four strokes, one systemic embolism and six instances of device-related thrombus by TEE.

Importantly, Reddy pointed out that the observed rate of ischemic stroke at 1.8 percent represents a 75 percent reduction from the expected event rate in patients with a similar CHADS2 score treated with aspirin alone (7.1 percent) and a 64 percent reduction vs. aspirin plus life-long clopidogrel (5 percent). He said that the stroke rates in this study were similar to those observed in the PROTECT AF study, which assessed similar subjects not contraindicated to warfarin.

The researchers concluded that the “first formal results from the largest study of LAA closure in patients contraindicated to warfarin demonstrate the Watchman may be an important alternative for high risk AF patients with limited options for stroke prevention.”

During his presentation, Reddy pointed to several additional questions that have yet to be answered based on the available data: How important is the 45 days of warfarin transition? How important is the six months of Plavix administration? “It is not clear that these drug regimens helped our outcomes,” he said.

“Following in that vein, the obvious next question is the importance of aspirin,” said Richard I. Fogel, MD, director of the cardiovascular disease fellowship program at St. Vincent Health in Indianapolis, who chaired the late-breaking trial session. “That’ll be the next study,” Reddy replied. 

Watchman was approved for marketing in Europe and other CE Mark countries in 2009. Researchers are currently enrolling U.S. patients in PREVAIL, a confirmatory study designed to gain FDA approval, according to the Natick, Mass.-based Boston Scientific. The FDA requested more information than the PROTECT AF study produced, leading to PREVAIL, in which enrollment is expected to be completed in the second quarter of 2012.

In the U.S., Watchman is an investigational device, limited by applicable law to investigational use and not available for sale. The device was developed by Atritech, which Boston Scientific acquired in March 2011