The safety of drug-coated stents — which prop open the arteries of about three million Americans and 40,000 Canadians — seems to depend on who is using them and how, a U.S. advisory panel said Thurday.

Panel members were speaking on the first day of hearings by the U.S. Food and Drug Administration into use of the stents — steel mesh tubes, about four millimetres wide, that are inserted into arteries to keep the vessels from reclosing after doctors have cleaned out plaque.

Coated stents cost about three times more than older, bare varieties.
(CBC)

The hearings, scheduled through Friday, focus on drug-coated types, designed to keep arteries open longer by preventing tissue from regrowing, compared with older, bare-metal stents.

When used as labelled, coated stents don't seem to increase the risk of heart attack or death but may increase the risk of blood clots, panel members said.

"The message is drug-eluting stents are safe and that the safety concerns are far outweighed by evident clinical benefit," panel chairman Dr. William Maisel, of Beth Israel Deaconess Medical Center in Boston, told reporters.

Another panel member, Dr. Steve Nissen of the Cleveland Clinic, said the magnitude of the clotting risk is in question.

A preliminary analysis by FDA staff concluded there is a rare but serious potential problem with drug-coated stents — patients seem to have more blood clots one to three years after the devices are inserted, compared with patient using the regular stents.

Boston Scientific Corp. has acknowledged there is a slight increase in blot clots associated with its drug-coated stent, called the Taxus. Johnson & Johnson has said there is no significant difference in clotting, heart attack or deaths rates between its coated stent, the Cypher, and the bare varieties.

The FDA has asked an outside panel of experts to review the safety data and advise on a wide range of questions surrounding coated stents, including whether to:

• Update the labels with new warnings.
• Identify patients for whom they are not appropriate.
• Perhaps change federal recommendations on how long people should take anti-clotting drugs such as Plavix and Aspirin following stent surgery.
• The agency also seeks recommendations for research on drug-coated stents on the market or pending approval.

Small risk to patients

In Canada, fewer coated stents are used because the provinces will only pay for a certain number. Drug-coated stents cost between $3,000 and $5,000 a piece, up to four times more than a bare stent.

Most Canadians undergo preventive drug therapy with anti-clotting drugs following stent procedures, the Heart and Stroke Foundation says. The anti-clotting drugs carry their own risk of causing internal bleeding.

Cardiologists say people with drug-coated stents should not worry because the blood clots are rare — happening in about one in 200 patients.

"When the drug-eluting stents first came out, all the patients were asking, 'Why can't I have it,' because we had to restrict the use of them," recalled Dr. Bradley Strauss, a cardiologist in Toronto. "Now, you're getting some people calling and saying, 'Why did I get it?' But I try to reassure them that the risk is small."

The problems only showed up after they had been widely implanted in patients.

Regulation of medical devices

Medical devices aren't as well-regulated as drugs in Canada or the U.S., said Dr. Salim Yusuf of McMaster University in Hamilton. In the last five years, 79 medical devices have been taken off the market in North America because of potentially deadly side effects.

"I think what drug-eluting stents have done, [they have] reduced the complication rates of a relatively benign problem, but [they have] increased the rates of a potentially life-threatening problem," said Yusuf.

Health Canada said it has a comprehensive approval process for medical devices and does all it can to ensure the safety of stents. The Canadian regulator is watching the FDA hearings and is assessing the safety of the devices.

With files from the Associated Press