Dec 11 (Reuters) - An advisory panel of medical experts voted on Wednesday to recommend that U.S. health regulators approve an experimental stroke-prevention device made by Boston Scientific Corp

The panel voted 13 to 1 that the benefits outweigh the risks of the Watchman device. The committee advised the U.S. Food and Drug Administration to approve the Watchman for the prevention of ischemic stroke and systemic embolism in patients with a dangerous cardiac rhythm known as atrial fibrillation.

People with atrial fibrillation, the most common type of arrhythmia, are five times more likely to suffer a stroke than those without the condition. It affects nearly 3 million people in the United States, and that number is expected to increase.

The FDA typically follows the recommendations of its expert advisory panels, but is not obligated to do so.

In documents prepared before the committee meeting, FDA staff members highlighted the implant's failure to meet a key goal for effectiveness in a recent study. But they said other data must be weighed in deciding whether it should be approved.

The device, implanted in the heart to prevent stroke in patients with atrial fibrillation, was developed as an alternative to clot-preventing blood thinners.

It is aimed at sparing heart patients a lifetime of taking anticoagulant drugs, such as warfarin, which carry a high risk of bleeding.

An FDA advisory panel recommended approval of the first-of-its-kind device in 2009, but the agency ultimately decided another study was needed to evaluate its safety and effectiveness.

Boston Scientific acquired the Watchman device when it bought Atritech in March 2011. It has been on the market in Europe since 2005.