HealthLINK: Cardiac: Coated stents help keep arteries open

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May 16, 2002

News this month
Coated stents help keep arteries open

At the 2002 American College of Cardiology's (ACC) annual meeting, physicians reported early success in preventing newly opened heart arteries from shutting again by using drug-coated versions of conventional stents. If similar results are obtained in larger, longer trials, almost all of the one million Americans who undergo angioplasties each year to open heart arteries could benefit.

Almost all Americans who undergo angioplasties to open heart arteries could benefit.

Angioplasty's limitations
Angioplasties are procedures in which a balloon-tipped catheter is inserted through the groin and up into the area of the arterial blockage. As the surgeon expands the balloon, the plaque is forced up against the arterial wall, opening the vessel. The problem: With angioplasty alone, about 40 to 50 percent of arteries reclog within six months.

Angioplasty + stent
This problem has been partially solved with the use of stents, which are miniature wire coils inserted at the time of angioplasty to keep arteries propped open. But even with stents, renarrowing occurs in about 25 percent of patients. Drug-coated stents, about eight varieties of which are currently being studied, are the latest attempt to avoid this complication.

Anti-rejection drugs key to keeping arteries open
Recent research focuses on stents coated with a variety of drugs designed to stop this process at various steps along the way. In two of the studies reported at the ACC conference, stents were coated with a potent immunosuppressive drug called sirolimus, used to prevent rejection in organ transplants.

Brazilian study
In reporting on one of the studies, Eduardo Sousa, MD, who heads the study based at the Institute Dante Pazzanese in Brazil, said none of the 30 patients followed in his study had renarrowing of the stented artery after two years; 80 percent had no excess development of scar tissue at all. While 20 percent did develop some scar tissue, Dr. Sousa said it was “minimal” and did not impede blood flow.

Before treatment, these patients had arteries that were 61 percent blocked. Immediately after insertion of the treated stent, the blockage was reduced to 4.2 percent and remained that way for the two-year follow-up period. Three of the patients needed heart procedures for worsening disease in other parts of their hearts, but not in the area where the stents were inserted.

French study
A second study, the RAVEL Trial, featured about 240 patients in France who were randomly assigned to receive either conventional stents or stents coated with sirolimus. One year after insertion of the stents, none of the arteries with the drug-coated stents had reclogged, compared with about one in four of those with conventional stents, reported Dr. Jean Fajadet of Clinique Pasteur in Toulouse, France.

None of the diabetic patients treated with coated stents had renarrowing compared with 42% for patients who had uncoated stents.

For patients with diabetes who have higher risks of complications, the contrast was even more dramatic. None of the diabetic patients treated with coated stents had renarrowing compared with 42 percent for patients who had uncoated stents.

Larger studies needed
There is still a way to go before the drug-coated stents are ready for general use. Physicians want to see the findings confirmed in larger studies. One such trial, of over 1,000 patients randomized to receive either sirolimus-coated stents or regular stents, is expected to be released by September. If all goes well, that device could be on the market by the end of 2002.

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Stent advances aid angioplasties

Drug-coated stents represent the biggest development in interventional cardiology care since angioplasties were first introduced.

Drug-coated stents may prevent renarrowing of the artery after angioplasty.

We've used stents for several years to prevent arteries from renarrowing after angioplasty, but about a quarter of patients need to have another angioplasty or coronary artery surgery to restore blood flow to the heart when scarlike tissue forms around the initial angioplasty site. Drug-coated stents look like they may be the solution to this problem.

Used extensively in Europe, drug-coated stents have not yet been approved by the Federal Drug Administration (FDA) in this country. However, Yale-New Haven Hospital is currently one of 55 American hospitals involved in a blinded, randomized study where—unknown to both doctor and patient during the procedure—some drug-coated stents are inserted into patients during angioplasties.

“One group has zero restenosis while the other group has about a 35 percent restenosis rate.”

The preliminary data from the studies in Europe, South America and the U.S. are amazing. Although we're not privy to which patients have the coated stents and which do not in the study we're participating in, it's pretty clear—one group has zero restenosis (renarrowing of the artery) while the other group has about a 35 percent restenosis rate.

How does it work?
The process of pressing a stent into the blood vessel wall is a kind of injury, and the body's immune system responds by creating scar tissue, especially in the days immediately after the procedure. The scar tissue results in a renarrowing of the artery, which can again block the flow of blood to the heart.

The drug on the stent is released over several days and interrupts the normal proliferation of scar tissue cells. It does not kill cells and instead allows the stent to be covered with the layer of smooth cells that normally line blood vessels. The development of these stents has particular importance for women who experience a higher rate of restenosis because of their smaller vessels.

The drug-coated stents may also help those patients with multiple blockages or long narrowing who had to have surgery in the past. In addition, diabetics may be helped by drug-coated stents because they can be candidates for angioplasty rather than surgery, which puts them at higher risk.

“It's very likely [drug-coated stents] will reduce the number of bypass surgeries and repeat angioplasties by 20-30%.”

Future prospects
The future of drug-coated stents is very promising. I fully expect the FDA will approve them when the results of longer-term, large studies are available. And although they will add to the cost of an angioplasty, it's very likely they'll reduce the number of bypass surgeries and repeat angioplasties patients need by 20 to 30 percent. Ultimately, drug-coated stents will most likely reduce the price of caring for patients with heart disease.

They will reduce risks as well, particularly for certain patients—the elderly, people with diabetes and women, who have a higher mortality rate during surgery and who have more extensive disease than men when they are diagnosed with cardiovascular disease.

Dr. Cleman is director of the Cardiac Catheterization Laboratory at the Yale-New Haven Heart Center and professor of medicine at the Yale University School of Medicine.