Florida ? Taking the blood thinner Plavix along with aspirin helped prevent strokes and heart attacks in people with a common heartbeat abnormality that puts them at high risk of these problems, doctors reported Tuesday.

The treatment is for atrial fibrillation, a rhythm disorder that 2.2 million Americans have. It occurs when the upper parts of the heart quiver instead of beating properly. This allows blood to pool and form clots that can travel to the brain, causing a stroke.

The usual treatment is the blood thinner warfarin, sold as Coumadin and in generic form. But finding the right dose is tricky — too little and patients can have a stroke; too much and they can have life-threatening bleeding. Patients on the drug must go to the doctor often for blood tests to monitor their dose.

For these reasons, as many as half of patients take aspirin instead of warfarin, even though aspirin is much less effective at preventing strokes.