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New devices keep arteries open
The also spur ethical, cost debate
New drug-eluting stents hold promise for people with narrowed arteries, but their cost raises concerns. Image courtesy of Cordis Corp.
GREENVILLE, N.C. (June 4, 2003) — A new type of stent that uses medication to stop the growth of scar tissue inside narrowed arteries propped open with the metal devices has been called a "major breakthrough" in the effort to reduce return visits by patients to cardiac catheterization labs. But doctors are also cautioning not to get one's hopes too high.
The new drug-eluting stents use chemotherapy or anti-rejection drugs to prevent cell multiplication. But just as not all narrowed arteries are created equal, not all patients will benefit from the new stents.
Cardiologists began using the stents at the Heart Center at Pitt County Memorial Hospital in late May. Some patients have already been asking for them.
"I've had patients asking about it for months," said Dr. Eric Carlson of Carolina Heart. He said he has several patients who are candidates for the stents.
At this point, however, the stents are not a cure-all for coronary artery disease.
"I view it as evolutionary, not revolutionary," said Dr. Joseph Babb, professor of medicine and chief of interventional cardiology at the Brody School of Medicine at East Carolina University. "I see it as another step down the road of technology improving patient outcomes."
Stents are tiny tubes made of a stainless-steel mesh used to hold open arteries that have narrowed due to plaque, scar tissue growth or other reasons. Cardiologists insert them by threading a tiny wire up through the patient's groin or arm and then opening them at the spot of the narrowing, or lesion. Stents are an advance from balloon angioplasty, where cardiologists thread a wire to the lesion and then inflate a balloon to compress the lesion against the artery wall. The downside is that the stents, since they are a foreign body inside the vessel, can trigger the growth of scar tissue, which can restrict the flow of blood through the artery. This scar tissue growth is called restenosis.
"The Achilles heel of angioplasty has always been the tendency toward recurrent narrowing, or restenosis," Babb said.
Dealing with this scar tissue may involve placing a second stent beside the first, using radiation to kill the tissue, a process known as brachytherapy, or, in severe cases, bypass surgery.
Drug-eluting stents are coated with a polymer, and then the drug is applied to the polymer. A third layer goes over the drug. Over several weeks, the drug then washes out, or elutes, and settles in the vessel wall, where it stops tissue growth from occurring inside the stent.
According to the Society for Cardiac Angiography and Interventions, candidates for drug-eluting stents have lesions up to approximately 30 millimeters long in vessels 2.5 to 3.5 millimeters in diameter. These criteria would include more than half of the blocked arteries in currently diagnosed heart patients. The stents have also been demonstrated to be very effective in traditionally high-risk patients, such as those with diabetes.
"The recent development of ... drug-eluting stents is a major breakthrough in preventing restenosis...," the society said in a paper. Babb served on the SCAI task force that wrote that paper.
Carlson agreed. "There's no doubt they represent a significant advance in the treatment of coronary artery disease," he said. "As time goes on, we're going to find they represent a big improvement in the tools" cardiologists have to treat narrowed arteries, he said.
In April, the Food and Drug Administration approved the first drug-eluting stent, a device made by Cordis, a subsidiairy of Johnson & Johnson. Boston Scientific is expected to hit the market with its own drug-eluting stent by the end of the year. The stents are now used in more than 60 countries worldwide.
"These new stents are another example of how the Heart Center strives to serve patients with the most innovative, up-to-date treatments and technology available,
East Carolina University
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