Patients who have received a drug-coated stent to prop open an artery face double the risk of heart attack or death after they stop taking an anti-clotting drug, researchers said Tuesday.
The findings mean patients may need to stay on medication beyond the three to six months currently recommended and possibly for the rest of their lives, scientists said.
The study, funded by the Department of Health and Human Services, was the latest to connect drug-coated stents to an increased risk of deadly blood clots. It was published online by the Journal of the American Medical Assn.
A Food and Drug Administration advisory committee is scheduled to meet Thursday and Friday to consider how to address mounting safety concerns. Among the questions the FDA wants answered is whether the devices are safe enough to remain on the market, and if so, how broadly they should be used.
The tiny wire-mesh tubes, coated with drugs to prevent scarring, have been given to about 3 million patients in the U.S. since their introduction in 2003, according to the FDA. Produced by both Boston Scientific Corp. and Johnson & Johnson, drug-coated stents have been a financial success, with total sales of $5.3 billion last year.
Stents are used to keep arteries open after fatty deposits have been cleared. During an angioplasty, a balloon-tipped catheter is threaded through a blood vessel to the site of the blockage. After the balloon is inflated to open the artery, a stent is positioned inside the vessel.
Drug-coated stents have become more common than older, bare-metal stents, which can cause scar tissue to accumulate and narrow the artery, a condition called restenosis. Although restenosis seldom leads to a heart attack, it can cause chest pain. In some cases, scarring is so great that patients need to have the vessel opened again.
The drug-coated stents, which prevent a buildup of scar tissue, have fulfilled the promise of reducing the need for repeat procedures. But as a result, they can prevent healing and create an environment conducive to clot formation.
Research conducted over the last two years has found coated stents carry a higher risk of life-threatening clots months or even years after the procedure, a condition called late-stent thrombosis.
Last week, researchers from the Cleveland Clinic reported in the American Journal of Medicine that clots were four to five times more likely to occur with coated stents than with the bare-metal variety. The hazard developed after patients stopped taking the anti-clotting drug Plavix, which is typically prescribed for three to six months.
Swiss researchers reported in the Journal of the American College of Cardiology on Monday that patients who stopped taking Plavix doubled their risk of heart attack or death compared with patients with bare-metal stents.
In the latest study, researchers at Duke University looked at 1,500 patients who received coated stents, comparing those who discontinued Plavix with others who stayed on the drug for at least six months.
After two years, those taking Plavix had a death or heart attack rate of three per 100, compared with seven per 100 for those no longer taking the anti-clotting drug, researchers said.
Researchers at Duke also looked at more than 3,100 patients who had received a bare-metal stent.
After two years, the rate of heart attack or death among patients with bare-metal stents was more than five per 100 -- worse than the coated stent patients who stayed on Plavix but better than those with coated stents who stopped the drugs.
"If you have a drug-eluting stent, it looks like not being on Plavix is a big problem," said Dr. Robert M. Califf of Duke, senior author of the study.
The results suggest patients with coated stents should remain on Plavix indefinitely, Califf said.
Dr. Matthias Pfisterer, a cardiologist who led the Swiss study, said long-term use of Plavix also entails risk. The anti-clotting drug causes severe bleeding in up to 2% of patients, he said, and is expensive at $4 a day.
Rising safety concerns have led hospitals to reduce their use of coated stents, which cost more than $2,000 each compared with about $700 for a bare-metal stent.
Dr. Spencer King, chairman of interventional cardiology at Fuqua Heart Center in Atlanta, reports a drop of 5% to 8% at his hospital. Patients who can't afford Plavix or will have to discontinue the drug because they need other surgery are not good candidates for coated stents, King said.
"Everyone is being more selective," he said.
Dr. Sanjay Kaul, a cardiologist at Cedars-Sinai Medical Center, said 70% of patients who received stents in September received the coated type, down from about 95% in January, and he expected usage to fall further.
Kaul said the root of the problem was that stents were overused. His research shows that 35% to 50% of patients who receive a coated stent don't need one.
Many patients who now get stents would benefit from drug therapy, such as beta blockers and cholesterol-lowering drugs, he said.
"Our obsession with restenosis begat the problems with stent thrombosis," he said. "It's time to take a step back."