The future is uncertain for a promising heart device aimed at preventing strokes in people at high risk because of an irregular heartbeat.

Early results from a key study of Boston Scientific’s Watchman device suggests it may not be better than a drug that is used now for preventing strokes.

More than 15 million people worldwide have atrial fibrillation.

That’s when the heart’s upper chambers quiver instead of beating properly.

This lets blood pool in a small pouch, where clots can form and cause a stroke.

The usual treatment is blood thinners, but some are very expensive.

The Watchman is intended to be a permanent solution that would not require people to take medications for the rest of their lives.

(The Associated Press)