Staying On Plavix May Cut Stent Risk

The blood thinner Plavix may reduce the rare but deadly risks of drug-coated stents, but major questions remain, according to new research.

Stents are tiny mesh tubes used to prop open an artery after a balloon angioplasty opens a clog.

Bare-metal stents sometimes clog. Newer, drug-coated (or drug-eluting) stents don't clog nearly as often. But they take much longer to heal — increasing the risk of a deadly blood clot.

That's why patients who get the newer stents get blood-thinning treatment with a combination of Plavix and aspirin. New data show that when treatment stops, problems start.

In one of the new studies, Swiss researchers Matthias Pfisterer, MD, and colleagues find that when patients stop taking Plavix, they have a small but serious risk of blood clots leading to death or heart attack.

"These side effects of drug-eluting stents are not frequent, but if they come, they may be heart attack or death," Pfisterer tells WebMD. But, he adds, "Patients should not be afraid of this treatment — the risk has been exaggerated."

Stent Benefit, Stent Risk

Pfisterer and colleagues calculate the risk this way: If 100 patients get drug-coated stents, five will avoid major cardiac events within six months.

But if they stop Plavix treatment at this time, three patients will suffer heart attacks or death in months seven to 18.

On the other hand, for every year they stay on Plavix/aspirin treatment, two out of 100 patients will suffer drug-related bleeding problems.

Even so, the blood-thinning treatment may be worth it, a second study — from Duke University — shows.

Eric L. Eisenstein, Robert M. Califf, MD, and colleagues followed 4,666 patients who got bare-metal or drug-coated stents.

They found that extending Plavix/aspirin treatment cuts the risk of heart attack and death associated with the drug-coated stents.

The data "suggest that all patients with drug-eluting stents should continue to take [Plavix] for at least 12 months after [stent implantation], and possibly indefinitely," Eisenstein and colleagues conclude.

That's also the opinion of Carolyn M. Clancy, MD, director of the U.S. Agency for Healthcare Research.

"This study suggests that patients and their physicians should consider extending the period of use of this therapy while monitoring its effects very carefully," Clancy says in a news release.

The Eisenstein study appears in the Dec. 5 issue of The Journal of the American Medical Association.

The Pfisterer study appears in the Dec. 19 issue of the Journal of the American College of Cardiology.

Urgent Need for More Data

The Swiss study's data come from a reanalysis of a 746-patient clinical trial.

That trial was designed to compare drug-coated stents with bare-metal ones — not to look at late-occurring side effects like clogged arteries. So Pfisterer warns the data can't be considered definitive.

"There is a lack of data — and we need that data," Pfisterer says. "We need to look at all these issues in more detail."

Major questions remain:

• Which patients need extended Plavix/aspirin treatment?
  
• What dose of Plavix is best?
  
• How long should Plavix/aspirin treatment continue?
  
• What, exactly, are the risks and benefits of extended Plavix/aspirin treatment?
  
• Are there patients who should not receive drug-coated stents?

"About two-thirds of our patients were really treated with off-label use of drug-eluting stents," Pfisterer says.

"The FDA label says these are only for stable patients with limited disease. But, in fact, most doctors who use drug-eluting stents use them in unstable patients and in more complex disease," says Pfisterer.

In an editorial accompanying the Pfisterer study, Califf and colleague Robert A. Harrington, MD, argue that clinical research on drug-eluting stents is not keeping up with clinical realities.

"As is frequently seen with new cardiac devices, rapid increase in clinical adoption [of drug-eluting stents] quickly outstripped what is known about the device from limited clinical trials," Harrington and Califf note.

The Swiss study and other recent data, the Duke researchers conclude, "have led us to the conclusion that patients with drug-eluting stents should remain on [Plavix] and aspirin if at all possible until adequate studies are completed."

This week, the FDA is convening an expert panel to discuss the safety issues swirling around drug-coated stents.

Heated debate is expected.

SOURCES: Eisenstein, E. The Journal of the American Medical Association, 2006; vol 297, early online edition. Pfisterer, M. Journal of the American College of Cardiology, Dec. 19, 2006; vol 48: pp 2584-2591. Harrington, R. and Califf, R. Journal of the American College of Cardiology, Dec. 19, 2006; vol 48: pp 2592-2595. News release, Agency for Healthcare Research and Quality. Matthias Pfisterer, MD, University Hospital, Basel, Switzerland.