Stents hold promise for cardiovascular patients

Press, 25 August 1987, Page 18

Stents hold promise for cardiovascular patients

By

RITA RUBIN

of NZPA-KRD Dallas

The smallest are as narrow as a thin spaghetti noodle and weigh the same as a pin, but a number of cardiovascular and cancer researchers say these half-inch tubes of stainless steel hold promise far greater than their size. In patients with cardiovascular disease these tubes — called stents — can expand narrowed arteries and improve blood flow without surgery, researchers say. In cancer patients, the stents can widen veins and other anatomical tubes squeezed by inoperable tumours or scar tissue from radiation therapy. The stents are attached to the end of a catheter, or long tube, inserted through the skin or into a body opening and threaded into the constricted passageway. While stents probably will never eliminate the need for coronary bypass surgery, the devices can be used to improve the outcome of a common, non-surgical method of expanding arteries called balloon angioplasty, researchers say. In medicine, “the tendency is to be less and less invasive,” said Dr Julio Palmaz, chief of special and vascular procedures in the radiology department at the University of Texas health science centre at San Antonio.

"These procedures have less complications than surgery.” Only Dr Palmaz’s stent has received approval from the United States Food and Drug Administration (F.D.A.) for multicentre testing in the United States. But several doctors have skirted federal regulations by cus-tom-making stents for use only in their own patients. Because of lessstringent regulation of medical devices abroad, stents have been more widely used in Europe. At the University of Lausanne in Switzerland, for example, stents have been inserted into the coronary arteries of more than 50 patients. The F.D.A. granted approval to test Dr Palmaz’s inflexible, mesh-like stent only in narrowed arteries in the lower extremities. Eventually, Dr Palmaz says, he hopes to receive permission to test the stent in coronary arteries, a riskier procedure. In May, before receiving F.D.A. approval to use the stent in the United States, Dr Palmaz placed one in a severely blocked pelvic artery of a man, aged 74, at the University of Freiberg medical centre in West Germany. Before the stent was inserted, the man could not walk more than a block without suffering painful cramps in his right leg because of restricted blood flow, Dr Palmaz said. After the stent was inserted the

man could walk a mile without pain. More recently, Dr Palmaz inserted the stent into the peripheral arteries of two more patients in Freiberg and one patient in San Antonio.

Dr Palmaz inserts the stent after performing balloon angioplasty in the artery. In that procedure, a balloon-tipped catheter is inserted into the artery. The balloon is then expanded to compress de? posits of cholesterol and other cells, called plaque, on artery walls. Only about 15,000 angioplasties were performed in peripheral arteries in the United States last year, and only onethird of those patients benefited, Mr Palmaz said.

“It is not as popular as it is in the coronary arteries,” he said. “Even in very experienced hands the results are not very clear.”

About 150,000 coronary angioplasties were performed last year in the United States. “The prob-

lem with balloon angioplasty is it really does not provide us with as much blood flow as stenting does,” Dr Palmaz said.

The elasticity of coronary arteries makes them tend to contract 30 per cent to 40 per cent right after angioplasty, he said, but “most of the time, it is enough to improve the patient.”

In three out of 10 patients, though, plaque deposits recur in coronary arteries six months to two years after angioplasty, Dr Palmaz said. These recurrences of plaque spurred researchers to look for ways to keep arteries open, including lasers as well as stents. “You either have to cut out tissue, bum out tissue, vapourise tissue or hold the artery wall back,” said Dr Simon Stertzer, the director of medical research at the San Francisco Heart Institute. While safer than surgery, angioplasty is not without risks. In two per

cent to five per cent of patients, coronary arteries collapse after angioplasty, resulting in the need to perform emergency bypass surgery, said Dr Gary Roubin, director of research at the Andreas Gruentzig cardiovascular centre at Emory University in Atlanta. Dr Roubin is awaiting F.D.A. permission to use a flexible, coil-shaped stent to reopen collapsed coronary arteries in angioplasty patients and prevent a heart attack from occurring before bypass surgery can be performed.

“I think the stent will make angioplasty much safer and more effective if it works, and every indication is that it will work. Ultimately, we hope we will not have to send the patients to bypass surgery,” he said.

The stent could not totally replace bypass surgery, because it cannot be inserted into arteriescompletelyblocked by plaque, Dr Roubin said.