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For Release After 11:30 a.m. CST, Monday, Dec. 1, 1997

CRITERIA USED TO DECIDE WHO GETS SURGERY TO PREVENT STROKE

MAY UNDERESTIMATE RISK IN WOMEN

CHICAGO -- Criteria commonly used to determine whether people at risk for stroke should have surgery or drug therapy may underestimate the risk in women, while overestimating it in men, according to information presented here today during the 83rd Scientific Assembly and Annual Meeting of the Radiological Society of North America (RSNA).

The criteria for deciding who needs surgery to open clogged carotid arteries in the neck -- a risk factor for stroke -- state that individuals of both sexes with blockages of 70 percent or greater may benefit from surgical intervention. Patients are usually treated with drugs until they reach that barrier.

Women's carotid arteries are smaller than men's, and using a one-size-fits-all 70 percent criteria does not take into account differences in size, according to Lisa Tartaglino, M.D., associate professor of radiology, Thomas Jefferson University Hospital, Philadelphia. "The size of the opening through which blood can flow in a small vessel that is 70 percent blocked is smaller than the opening of a larger vessel that is 70 percent blocked," she said.

The criteria were established by the North American Symptomatic Carotid Endarterectomy Trial (NASCET) based on a ratio of the internal diameter of the blocked artery at its narrowest divided by the normal diameter of the blood vessel, said Dr. Tartaglino. "The NASCET trial was halted for the category of patients with greater than 70 percent stenosis when it was determined that patients with blockage of 70 percent or greater may benefit from endarterectomy -- a surgical treatment. Approximately 100,000 people undergo the surgery in the United States each year," she said.

"Because the NASCET criteria is a ratio measurement, the denominator in the equation is almost always smaller for women. When the blockage reaches 70 percent in a woman, the absolute size of the narrowing through which blood flows to the brain is also smaller."

Dr. Tartaglino and her colleagues used computed tomography (CT) angiography to image 40 patients -- 21 men and 19 women -- who had been identified by ultrasound to have carotid artery disease. "Men and women differed in the average size of their carotid arteries by a minimum of 10 percent to 15 percent," she said.

"These observations suggest that if we continue to use a ratio, we should consider using a different percentage of blockage to determine the threshold at which women and men need surgical treatment. If we go to an absolute measurement of vessel narrowing, then it may not matter," Dr. Tartaglino said. Further studies with larger numbers of patients are needed to verify these findings, she said.

Co-authors of a paper on the topic presented by Dr. Tartaglino during the RSNA meeting are M. Hollander, M.D.; L. Needleman, M.D.; A. Flanders, M.D.; R. Bell, M.D.; and M. Kahn, M.D., all from the cerebral vascular center at Thomas Jefferson University.

The RSNA is an association of 30,000 radiologists and physicists in medicine dedicated to education and research in the science of radiology. The Society's headquarters are located at 2021 Spring Road, Suite 600, Oak Brook, Illinois 60523-1860.

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Copies of 1997 RSNA news releases are available online at http://www.pcipr.com/rsna beginning Monday, Dec. 1.