Sunnybrook and Women's College Health Sciences Centre

Sunnybrook and Women's College Health Sciences Centre

September 29, 2005 09:34 ET

New findings correct common pitfalls in assessing risk of stroke

Attention: Assignment Editor, Health/Medical Editor, Media Editor, Science Editor TORONTO/ONTARIO--(CCNMatthews - Sept. 29, 2005) - Researchers at Sunnybrook & Women's are suggesting new criteria that will help physicians find narrowing in the artery beyond the site of the disease which will help determine the best type of treatment to prevent possible stroke.

In most cases the usual method of diagnosis is to zero in on the diseased area but these suggestions will help physicians to look for narrowing in other parts of the artery that may not be as obvious but could mislead the impressions of the risks contributing to stroke.

"These clues will help physicians find other contributors to stroke and determine the best possible method of treatment," says Dr. Allan Fox, principal investigator of the study and Neuroradiologist in Medical Imaging at Sunnybrook and Women's College Health Sciences Centre. "While surgical intervention is one method of treating a diseased carotid (neck) artery, other treatments may be more beneficial for arteries with narrowing in a different location other than the disease site itself."

Carotid disease occurs when the main artery of the neck that brings blood to the brain becomes narrowed or blocked by plaque, which can cause a stroke. Near occlusion is a reduction of the artery diameter or a collapse of the artery beyond the initial diseased narrowing, and occlusion is a complete blockage or obstruction in the artery, resulting in a stroke. "We found it is important to identify any other narrowing, regardless of its severity because it differs from other severe stenoses (artery narrowing) not just in appearance, but also for clinical outcome expectations from treatment," says Dr. Fox, also a professor at University of Toronto.

The criteria developed for testing included identifying the arrival time of an applied contrast dye in the carotid artery and seeking where it goes, comparing any reduction of diameter reduction in an artery width in different locations, and comparing the main carotid artery to a smaller artery to identify any similarities in diameter which may raise a red flag.

The study, published in the September 2005 issue of the American Journal of Neuroradiology, combined cases from two major international studies and attempted to compare which patients would benefit most from a surgical intervention versus medication alone. Endarterectomy is a surgical procedure to remove a potentially dangerous plaque from the carotid artery in the neck, clearing the obstructed artery to avoid a potential stroke.

The North American study (NASCET) recognized that near occlusion cases would produce flawed percentages if measured like other narrowing. Sunnybrook & Women's was a participating centre to this international, multi-centre trial. The study investigators then established the new criteria for recognition of near occlusion, and conducted in-depth testing by evaluating imaging tools such as angiograms to provide evidence for any narrowing or occlusion, and categorized them.

Unfortunately, the data did not lead to absolute conclusions about the benefit of endarterectomy for near occlusions but it did provide more evidence to suggest that specific kinds of carotid disease appear to be better treated with medication versus surgery. The outcome results suggest that endarterectomy is of less value for patients with near occlusion than for patients with severe stenosis but without near occlusion; therefore it is critical to identify the differences.

"The data do not support surgery for near occlusion patients, nor specifically prove against it, but suggest that the benefits and risks must be thoroughly assessed as possible benefits are muted," says Dr. Fox. "It is therefore crucial to identify near occlusions using these specific criteria."
Until now, there was no complete set of criteria for physicians to use to consistently identify patients with near occlusion.

Sunnybrook and Women's College Health Sciences Centre is transforming health care through the dedication of its more than 10,000 staff members and volunteers. Specializing in women's health programs, caring for Canada's war veterans, conducting leading-edge research, and teaching the latest advances in healthcare through our affiliation with the University of Toronto, distinguishes Sunnybrook & Women's as one of the country's premier academic health sciences centres. Sunnybrook & Women's improves the lives of hundreds of thousands of people each year by caring for newborns, adults and the elderly, treating and preventing cancer, heart and circulation diseases, disorders of the brain, mind and nervous system, orthopaedic and arthritic conditions, and traumatic injuries.
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