May 12, 2003

New stent defeats angioplasty's 'Achilles heel'

By Sherry Baker

The U.S. Food and Drug Administration recently approved a new type of drug-eluting coronary stent, developed in part through research at the Emory Heart Center, that has been shown to greatly reduce restenosis (reclogging of arteries) following angioplasty.

Called “Cypher” stents and produced by the Cordis Corp., the stents release a drug called sirolimus as they prop open arteries; they are the first U.S.-approved combination drug and stenting device intended to help reduce restenosis of a treated coronary artery.

Angioplasty is the most common procedure in the United States to treat potentially life-threatening coronary blockages. During angioplasty, a balloon-tipped catheter is used to push aside atherosclerotic plaques in arteries. Once the vessel has been widened, adequate blood flow returns and stents (tiny mesh wire tubes) are frequently used to keep arteries open.

However, restenosis has proven to be a frequent problem, and patients who suffer from it may require additional medical procedures. For many people, the new drug-eluting stents could offer a potential solution to restenosis, which has been called the “Achilles heel” of angioplasty.

The stents were tested in a study at the Emory Heart Center and 52 other U.S. medical centers. In the randomized, double-blind clinical trial involving 1,058 patients, the Cypher stents were found to greatly reduce restenosis compared to conventional stents.

“We believe these drug-eluting stents will be a major breakthrough in defeating restenosis after stenting,” said John Douglas, professor of cardiology and primary clinical investigator for the Emory study.

In the trial, patients received either a plain metal stent or a Cypher stent coated with sirolimus. “At eight-month angiographic follow-up, patients treated with the Cypher stent had an overall 75 percent reduction in restenosis when compared to the control group,” said Ziyad Ghazzal, associate professor of cardiology and study co-investigator.

“In the particular subset of arteries tests, the success rate of the drug-eluting stents was even more dramatic, with a success rate of more than 90 percent over conventional, bare metal stents,” said Douglas Morris, director of the Emory Heart Center. “We are proud that Emory was one of the sites in the United States for this extremely important multicenter study. I see the drug-eluting stent as a major advance in the treatment of coronary artery disease. It should lead to a profound reduction in restenosis, which is the primary deterrent to the even more widespread applicability of coronary stents.”

The stent’s sirolimus coating does not kill cells but allows the endothelium (the layer of cells lining vessel walls and the heart) to cover the stent. “This is important because the stent becomes coated with cells and incorporated into the heart,” said Douglas, who along with Emory colleagues implanted the country’s first coronary artery stent at Emory Hospital in 1987. Today, three-fourths of all patients undergoing angioplasties receive stents.

Without this cell covering, Douglas added, a stent may promote blood clot formation when the body “reads” the device as foreign material. “In fact, that’s one of the limitations of radiation treatment for preventing the renarrowing process in arteries,” he said. “Radiation prevents the growth of tissue over the stent, and that can up the risk for blood clot formation there later and lead to heart attack. The drug-eluting stent appears to be a solution to this problem.”

“We hope the approval of the Cypher stents will expand the horizon of percutaneous coronary interventions to include more patients that we can help,” Ghazzal said.