Jan. 16 (Bloomberg) -- Patients who receive drug-coated stents to prop open diseased coronary arteries should take blood thinners for at least a year to prevent deadly heart attacks, doctors from five medical societies said.

A U.S. advisory panel last month declined to suggest that the U.S. Food and Drug Administration change current instructions for patients to take aspirin and either the blood- thinner Plavix, made by Bristol-Myers Squibb Co., or Ticlid, made by Roche Holding AG, for up to six months.

Patients who quit the drugs prematurely are more likely to develop blood clots inside the stent and suffer fatal heart attacks, the groups said in a report published today by the American Heart Association in the journal Circulation. The evidence is beyond debate, said Raymond Gibbons, president of the largest U.S. group of cardiac specialists.

``We're concerned that this is a basic quality-of-care issue that has been overlooked,'' Gibbons said in a telephone interview today. ``People are having heart attacks and dying as a result.''

Plavix was the No. 2 drug in the world last year with sales of $6.3 billion. Heart patients who cannot afford the $4-a-day drug, or who prefer not to use it, should advise their doctors who can consider giving them uncoated stents that are less likely to cause blood clots, the joint statement said.

Plavix Safety

Some doctors have said the clot-preventing drugs should be taken for years, or until more is known about the long-term safety of drug-coated stents. The safety of taking Plavix for years has not been established either, scientists said.

There are two models of drug-coated stents approved in the U.S., the Cypher made by Johnson & Johnson and Boston Scientific Corp.'s Taxus. The companies dominate the $6 billion-a-year market for the products, and since their introduction in Europe five years ago, more than 6 million stents have been implanted, often with more than one stent per patient. Each stent sells for about $2,200.

Dentists and surgeons should consult with stent patients' heart specialists before advising them to discontinue Plavix or Ticlid because of the risk of bleeding after a dental or surgical procedure, the medical groups said. Such procedures should be delayed for a year, or patients should at least continue taking aspirin alone until the risks subside, the groups said.

Mesh Tube

A stent is a wire mesh tube used to prop open a previously blocked blood vessel. The stent is put into place with tubes and wires threaded to the heart through an artery opened above the thigh. Stents are designed to remain in place permanently to hold open the vessel and improve blood circulation.

A major problem with uncoated, or bare-metal, stents is the buildup of scar tissue inside it. If too much tissue develops, doctors can go back and reopen the vessel by widening it again or implanting a new stent within the original one.

Drug-coated stents were invented to slowly release medicine that prevents the re-blocking of the artery from excessive scar tissue. The danger with that approach is that the drug coatings may be so effective at suppressing tissue growth that they leave the wire mesh struts exposed to passing blood and cause clots.

Studies reported by European researchers in September found that 2.9 percent of patients with Cypher and Taxus drug-coated heart stents develop blood clots after three years, more than with bare-metal stents, and that the rate may keep rising.

Risk of Clots

A Cleveland Clinic study published in November found that the drug-coated devices raise the risk of clots as much as fivefold compared with bare-metal stents.

Shares of New Brunswick, New Jersey-based Johnson & Johnson fell 10 cents to $66.54 in New York Stock Exchange composite trading. They climbed 5.9 percent in 2006. Boston Scientific, based in Natick, Massachusetts, fell 9 cents to $18.12. The stock dropped 28 percent in the last 12 months.

Shares of Medtronic Inc., which makes a drug-coated stent sold in Europe and submitted for approval in the U.S., rose 79 cents, or 1.5 percent, to $54.51.

Shares of New York-based Bristol-Myers rose 32 cents to $26.57, while American depositary receipts of Paris-based Sanofi rose 2 cents to $45.67. One Sanofi ADR equals half a common share.

Limited available data indicates blood clots appears to occur at a higher rate in patients with conditions that aren't approved for U.S. use, such as diabetes or a history of heart attack, the panel said.

Off-Label Use

Some experts say doctors too often put stents in such patients, cases that are referred to as ``off-label'' uses. Some experts estimate that 75 percent of drug-coated stent implants are for off-label uses.

Some researchers reported that Plavix fails to offer long- term protection from clots. Plavix is a ``Band-Aid solution'' that may not work for many patients, said Sanjay Kaul, a University of California researcher who in October estimated that 2,160 deaths a year in the U.S. can be attributed to clots in drug-coated stents.

Several medical groups and consumer advocates say stents often are implanted in patients without informed consent when patients are sedated, and that patients don't understand the risks or receive help in managing their Plavix use.

Cardiac surgeons say too many patients are improperly persuaded by stent-implanting doctors to try stents to solve their circulatory problems because they want to open-heart surgery. They urged the FDA to directly compare the effectiveness of coronary bypass surgery to stents.

The groups issuing the advice today are the American Heart Association, the American College of Cardiology, the Society for Cardiovascular Angiography and Interventions, the American College of Surgeons and the American Dental Association.

To contact the reporter on this story: Avram Goldstein in Washington at agoldstein1@bloomberg.net.

Last Updated: January 16, 2007 16:54 EST