* FDA advisors recommend approval in 7-5 vote
* Some panelists still questions safety, effectiveness
* Panel says more study needed if approved (Adds comments from panel, background on device)
By Susan Heavey
WASHINGTON, April 23 (Reuters) - A U.S. Food and Drug Administration advisory panel on Thursday narrowly backed Atritech Inc's experimental device to prevent strokes in patients with irregular heart beat.
In a 7-5 vote, the FDA panel of outside experts said the device, called the Watchman, should be approved despite some lingering concerns over some of the data as well as possible complications.
The privately held device maker is seeking U.S. approval to market its coin-sized, cage-like device as a competitor to the widely used blood-thinning drug warfarin. It aims to prevent harmful blood clots that can enter the blood stream and cause stroke in patients with abnormal heart beat, or atrial fibrillation.
If its device is successful, the Minnesota-based company could become an acquisition target by larger medical technology companies, some stock analysts have speculated.
Warfarin, available as a generic and as Bristol-Myers Squibb Co's (BMY.N) branded drug Coumadin, is relatively inexpensive but can cause significant bleeding risk and patients must be frequently monitored. Several drugmakers, including Johnson & Johnson (JNJ.N) and Bayer AG's BAYG.DE, are also developing alternatives.
Norman Kato, a panelist and California-based physician, said he voted in favor of Atritech's device "with a lot of trepidation."
"I still am very, very concerned about the small sample size" of patients in the company's clinical trial, he added.
While Atritech studied 707 patients with atrial fibrillation -- 463 were given the Watchman and 244 patients given warfarin -- millions more could eligible for it in the wider marketplace, Kato and others panel members noted.
About 2.2 million Americans have the heart rhythm disorder, according to the American Heart Association.
If the FDA were to approve the device, panelists urged the agency to require the company to conduct longer follow-up studies for up to five years and takes steps to ensure surgeons are properly trained.
Atritech's expandable device ranges from the size of a penny to a half-dollar coin and is inserted near the heart's left atrial appendage where most clots are formed, according to Atritech.
Panelists said previously released data from a company-sponsored trial showed the Watchman comparable to warfarin but noted the potential for surgical-related complications and other safety issues.
The FDA will weigh the panel's vote before making its final approval decision. It usually, but not always, follows the recommendation of its outside experts. (Reporting by Susan Heavey; editing by Richard Chang)