Alford Dangas, an associate professor of medicine at Columbia University Medical Center in New York City, said during a morning teleconference at the American College of Cardiology's annual scientific sessions in Orlando, Fla. Bare metal stents -- as the name implies -- are bare tubes of metal mesh.

Drug-eluting stents, in addition to keeping the artery open, slowly release a medication to prevent the build-up of scar tissue inside the stent. After a heart attack, many patients undergo a treatment called angioplasty, which opens the blocked coronary artery that caused the attack. With many of these procedures, the stent, a metallic mesh tube that props open the narro artery, is also inserted and left in place.

"We had a thrombosis rate of 3.3% over a year, which sounds high, but these are patients with acute [heart attacks] getting a stent," lead researcher Dr. A stent thrombosis can block blood flow through the stent and cause another heart attack or even death. "So it's not that high after all." "With any type of bare metal stent or drug-eluting stent, there was no difference after one year," Dangas added.

Concerns have been raised that stent thrombosis might be more com in drug-eluting stents than.