Heart patients with drug-eluting stents implanted to keep their arteries open were found to have a much higher risk of sudden death than those getting bare metal stents if they stopped taking the blood thinner Plavix, a new Swiss study reports.

The study of 746 people who had 1,113 stents implanted did show that drug-eluting stents did a better job of keeping arteries open.

But the risk for patients with drug-eluting stents who stopped taking Plavix seven to 18 months after angioplasty was clear. The incidence of death or heart attack for those patients was 4.9 percent, compared to 1.39 percent for patients with bare metal stents. The reason was a higher incidence of thrombosis, which is sudden blockage of an artery by a blood clot.

But in doing so, the drug-eluting stents may also prevent the regrowth of the normal tissue that lines the artery, increasing the risk of thrombosis, Bonow said. Plavix can counter that risk, he said.

"Until we know more, any cardiologist would recommend continued use of clopidegrel," Bonow said.

"The uncertainty is how long we keep people on Plavix, indefinitely or for the first two years."

Kao's recommendation for Plavix use by people who get drug-eluting stents is "at least a year, indefinitely if they can afford it."

People faced with angioplasty should be aware of "the upside and downside of a drug-eluting stent," Bonow said. "With Plavix, it usually is a risk worth taking."

[Drug-eluting] stents may raise the risk of life-threatening blood clots months and even years later unless people stay on Plavix, an anti-clotting drug whose long-term safety in stent patients has not been established.

Doctors also worry about overreacting to a risk that appears small -- five or fewer clots in every 1,000 patients.

"The benefit of having a drug-eluting stent is tremendous," said Dr. Elizabeth Nabel, director of the National Heart, Lung and Blood Institute.

Now it seems the coated stents may keep this essential artery lining from forming for a long time, maybe permanently. Without the lining or Plavix, clots can form and stick to stents.

Bombshell finding that patients with coated stents had double the risk of cardiac problems after stopping Plavix than those with plain metal stents.

Deaths and heart attacks were higher with coated stents after three years and that their advantage for preventing artery reclosure disappeared by that time. Doctors in the Netherlands found that the devices were comparable after three years.

Coated stents had five times the risk of clots as plain metal ones.

Some doctors say stents were approved based on studies that were too small, too short and in low-risk patients.

Longer Plavix treatment now is being urged "a little bit to get the doctor off the hook," said Dr. David Williams of Brown University. "We're saying indefinite for some patients even though we have no idea what that means" in terms of safety, he acknowledged.

Requiring coated stent patients to take it indefinitely puts them at risk of a clot if they have to temporarily stop Plavix to prevent excessive bleeding

"There's a risk that's there when you don't have (Plavix). What we don't have are studies that show what's the risk with it,"