Melt-Away Stent Works Well in Trial

THURSDAY March 13, 2008 -- A polymer stent that is quietly absorbed by the body after it has done its job of keeping a coronary artery open has worked well in an international trial, researchers report.

The stent was successfully implanted in 29 of 31 attempts, the report said. In a one-year follow-up, none of the arteries in which the bio-absorbable stent had been implanted had closed again. One of the 30 people given the stent had a heart attack during that time, but no other adverse events were reported, according to the report in the March 15 issue of The Lancet.

A major clinical trial of the experimental stent is under way in several countries, said Karin Bauer, a spokeswoman for Abbott Laboratories, the company that developed the device. Plans for a U.S. trial are in the preliminary stages, she said.

"We currently are looking at the safety and feasibility of using the bio-absorbable stent platform in patients here," Bauer said. "Once we have completed the international trial, we will look at the feasibility of bringing such a trial to the United States, but we haven't made any decision as to when that might be."

The new stent has a backbone of lactic acid. It also is coated with everolimus, a drug that prevents formation of scar tissue.

Traditional stents are wire metal mesh tubes used to prop open an artery during angioplasty, a procedure done to clear blockages from the blood vessel.

An absorbable stent has many potential advantages, said Dr. Patrick W. Serruys, a professor of medicine and interventional cardiology at Erasmus Medical Center in Rotterdam, the Netherlands, one site of the international trial. Other sites are located in Denmark, Poland and New Zealand.

"The so-called restenosis process takes place in the first six months, so there is no need to have a permanent scaffolding device," Serruys explained. Restenosis is the reclosing of an artery, which can occur after a metal stent is implanted.

The polymer of which the Abbott stent is made breaks down to form carbon dioxide and water, "so you don't have a permanent foreign body in the blood vessel," he said. "That gives you more flexibility in the vessel. And some metallic stents are breaking, and the fracture of the metal creates some unpleasant reactions."

Because the polymer stent disappears, "many years later you are still able to work on the vessel," Serruys added. "You don't have a metallic cage that limits expansion of the vessel."

But there is a need for long-term follow-up of the experimental stent, he said, adding, "probably five or seven years down the road. Whenever you have a long-term follow-up, you can make a second attempt with the design. It will be a long process."

Still, Serruys said he was "impressed and amazed by the fact that the first attempt was so successful."

A second trial of a new version of the stent is in the planning stage, said study co-investigator Dr. John A. Ormiston, one of New Zealand's top interventional cardiologists and president of the Asia-Pacific Society of Interventional Cardiology. It will be done at the same sites as the first study, and will also have 30 stent recipients.

"There have been important design modifications," Ormiston said of the stent in the new trial. "The scaffold will be different so that it will be stronger. We think we might get even better results than we've had so far."

The trial could begin later this year. If it succeeds, it would be the prelude to a larger international trial that could lead to approval of the new stent for medical use, Ormiston said.

Posted: March 2008


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