Promising Heart Technology Hits a Snag
Success of one drug-coated stent fizzles rapidly
MONDAY, April 1, 2002 (HealthDayNews) -- Perhaps the hottest prospect in cardiology today is the idea of keeping arteries open with a coated stent -- a tiny tube that releases chemicals that limit the regrowth of vessel-blocking cells.
Even the American Heart Association describes the device as the greatest advance of 2001, saying it "could become one of the biggest breakthroughs in treating cardiovascular disease."
However, a new Italian study seems to cast a shadow on that prediction.
The performance of one type of coated stent in a special group of patients, while excellent after six months, deteriorated rapidly after one year, researchers found. In fact, most of the patients got restenosis -- reblockage of the treated arteries.
However, the finding, reported in tomorrow's issue of Circulation, "absolutely does not" apply to all coated stents and all patients, says lead author Dr. Antonio Colombo, chief of invasive cardiology at Emo Centro Cuore Columbus Hospital in Milan, Italy.
First, the stent used in the study was coated with a very thick plastic polymer, different from those of many other stents, Colombo says. "It could have been a reaction to the polymer" that caused the arteries to close, he explains.
Second, the stents were implanted in a small group of patients, 15 in all, who already had conventional stents implanted after angioplasty, an artery-opening procedure, and whose arteries had begun to become blocked again. In the great majority of other cases, the stents are implanted immediately after angioplasty.
"We were dealing with patients who already had restenosis," Colombo says. "In these patients, maybe the lesions are more likely to recur. So, we have two new factors. One is the plastic polymer, the other is the kind of lesions that were treated."
The stent used in Milan releases paclitaxel, a drug that inhibits growth of the cells that line the interior of arteries. Another such drug used in coated stents is serolimus.
A study of 245 patients reported last September at the meeting of the European College of Cardiology in Stockholm said none of the patients given the serolimus-coated stent after angioplasty had restenosis after four to six months, compared to 26 percent in patients receiving conventional stents. Only 3.3 percent of the patients given the coated stents had major cardiac events such as heart attacks, compared to 27 percent of those with the conventional stents.
Such reports are behind the enthusiasm for coated stents. However, there are fears the effects of the growth-inhibiting chemicals may wear off in time. Some other studies on the benefits of coated stents implanted right after angioplasty have shown good results after more than a year of follow-up, Colombo says, but he adds the new study does have lessons for cardiologists.
"One is the need not to be enthusiastic based only on six months' results," he says. "You need at least one year. Another is that every lesion is not the same. Success on simple lesions in patients without diabetes does not extrapolate to success in all lesions. So, not all stents are the same. And a length of follow-up of at least one year is very important."
While the Italian study was small, "it suggests we need to learn more about the way we coat stents, and the medications which we use to coat stents," says Dr. Sidney Smith, chief scientific officer of the American Heart Association.
Some caution may be needed, Smith says. "But anyone in the field of stents that is not seriously looking at a drug-eluting [releasing] stent is in danger of falling far behind," he stresses.
Also, a one-year follow-up of the European study shows continuing good results, he adds.
What To Do
Coated stents are not yet approved for general use in the United States and Europe. While European approval could come this year if early results stand up, U.S. Food and Drug Administration approval for use in this country is not expected until next year.