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Next Generation of Stents Responds to Problems

Newer drug-eluting and biodegradable versions show promise

SATURDAY, March 24, 2007 (HealthDay News) -- A new generation of stents, created largely to address problems associated with the current artery-opening devices, made their debut during the American College of Cardiology meeting in New Orleans Saturday.

These new stents attempt to ward off restenosis, the reclosing of a stented vessel, and thrombosis, the dangerous clotting that has been seen mostly in drug-eluting stents. The innovations ranged from coating stents with different and better drugs to building biodegradable stents that dissolve over time.

In one study, researchers compared the standard paclitaxel-eluting stent with a new drug-eluting stent called Xience V. Dr. Gregg W. Stone, director of Cardiovascular Research and Education at Columbia University Medical Center, and his colleagues randomly assigned 1,002 patients to receive stents with either Xience V or the standard drug-eluting stent.

"This is a second-generation drug-eluting stent," Stone said. "This trial was designed to get approval for this stent in the United States."

Stone's team found that after nine months, patients treated with the newer stent had similar rates of failure in the treated blood vessel, but needed fewer new procedures. There were fewer major cardiac events at nine months among patients treated with the XIENCE V compared with the standard drug-eluting stent (4.6 percent vs. 8.1 percent).

The new stent also decreased blood vessel loss and tended to reduce the re-blocking of the treated arteries compared with the standard drug-eluting stent (4.7 percent vs. 8.9 percent), Stone's group reported.

"This stent is at least as safe and effective and, for several of the important endpoints, is superior to the standard drug-eluting stent," Stone said.

Two other studies presented at the meeting by teams of Dutch researchers were on the cutting edge of stent development.

In the first, Dr. Marcel Beijk, from the University of Amsterdam, and his colleagues treated 152 patients with a stent coated with an antibody that attracted the endothelial cells that line blood vessels, and speeded healing. Before the stents were put in place, the patients had two weeks of statin therapy to increase the number of endothelial cells, Beijk explained.

"This accelerated healing may reduce restenosis, and may prevent stent thrombosis," he added.

Over six months, there was one death, one patient had a heart attack, three patients needed further procedures on the stented artery, and one needed stenting in another artery.

"While this is still an early study, it offers a whole new look at the use of stents and the process of healing damaged tissue throughout the body," Beijk said in a prepared statement. "As we look at new treatment combinations, we believe this is a step in the right direction to offer patients better long-term success rates."

In the other study, Dr. Patrick W. Serruys, a professor of interventional cardiology at Erasmus University, in Rotterdam, and his colleagues tested a biodegradable stent that is expected to disintegrate over time.

"Through Mother Nature, the backbone of the stent is completely digested and metabolized," Serruys explained. "This is a drug-eluting stent where the structure is going to disappear with time."

The potential advantage of such a stent is that it may reduce stent thrombosis, and make it easier to perform new stenting procedures on the same blood vessel. In addition, it may also make it easier to take an MRI or CT scan of the stented vessel, the researchers noted.

Early results were promising for the 30 patients who received the biodegradable stent. After 30 days, the stent appeared to be safe and effective. "These stents behave very much like a metallic stent," Serruys said.

There were no cases of stent thrombosis or restenosis, Serruys added.

Serruys noted that the length of time for the stent to dissolve isn't yet known, because that was the first time it has been used in people.

"In animals, it takes about 18 months," he said.

It will be years before such a stent is used in regular treatment, Serruys added. In addition, problems with the stent have sent the researchers back to the drawing board to redesign it.

In another study, Danish researchers showed that once blood-thinning therapy is stopped, drug-eluting stents could be linked to a higher risk of heart attack and stent thrombosis than bare metal stents are.

In the trial, led by Dr. Michael Maeng, from the department of cardiology at Aarhus University Hospital, Skejby, 12,395 patients received either drug-eluting stents or bare metal stents.

"Recent reports have indicated a potential increased risk of stent thrombosis, myocardial infarction and death with the use of drug-eluting stents," Maeng said.

Over 12 months, Maeng's group found that, while the rates of restenosis were significantly lower among patients receiving drug-eluting stents, the rates of heart attack and stent thrombosis were similar in both groups.

However, between 12 and 15 months, after blood-thinning drugs were stopped, there was a small but significant trend toward a higher risk of heart attack and stent thrombosis among patients who received drug-eluting stents.

"The follow-up period of 15 months may be insufficient to quantify risk with drug-eluting stents," Maeng said. "Drug-eluting stents are as safe as bare metal stents, at least up to 15 months after implantation."

More information

For more information on stents, visit the American Heart Association.

SOURCES: Gregg W. Stone, M.D., director, Cardiovascular Research and Education, Columbia University Medical Center, New York City; Michael Maeng, M.D., department of cardiology, Aarhus University Hospital, Skejby, Denmark; Marcel Beijk, M.D., University of Amsterdam, the Netherlands; Patrick W. Serruys, M.D., professor of interventional cardiology, Erasmus University, Rotterdam, the Netherlands; March 24, 2007, presentations, American College of Cardiology meeting, New Orleans
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