News Release

Bleed-detecting MRI may identify dangerous plaque

American Heart Association rapid access journal report

Peer-Reviewed Publication

American Heart Association

DALLAS, June 10 – A magnetic resonance imaging (MRI) technique that evaluates bleeding within plaque-clogged arteries may warn of an impending stroke or heart attack, according to two studies published in today’s rapid access issue of Circulation: Journal of the American Heart Association.

These are the first human studies of complicated plaque using MRI to specifically detect intraplaque bleeding in order to identify dangerous plaque. Plaque within blood vessels is a progressive disease that, in the early phase, causes minor vessel narrowing and usually has no symptoms. However, a plaque deposit becomes complicated when its surface cap has ruptured, there is bleeding inside the deposit or causes clotting within the artery where it has formed. Complicated plaque increases the risk of stroke or heart attack regardless of how much plaque is in the artery.

“Complicated plaque identifies disease that has already declared itself as dangerous,” says Alan R. Moody, M.D., radiologist in chief at Sunnybrook and Women’s College Health Sciences Center in Toronto and author of the two Circulation reports.

In these studies, MRI detected high-risk complicated plaque in the neck arteries of 60 percent of a group of patients who had signs and symptoms that often precede stroke. Researchers found no complicated plaque in any neck arteries of a healthy control group.

“Detection of complicated plaque in people without symptoms may provide an opportunity to intervene,” Moody says. “A number of drugs are now available that appear to stabilize plaque or reduce clot-related complications. If we can identify dangerous plaque, these drugs may be able to stabilize plaque before symptoms begin.”

Other imaging techniques have been used to evaluate the carotid arteries, including ultrasound, angiography, computed tomography and positron emission tomography. But all have limitations that make them less than ideal for routine use, Moody says.

“MRI is non-invasive, non-operator dependent, has the ability to perform angiography, and can characterize the overlying plaque cap and the extent of the underlying lipid pool – two factors that affect plaque stability,” he says.

The first study published by Moody and associates at University Hospital in Nottiingham, United Kingdom, confirmed that magnetic resonance direct thrombus imaging (MRDTI), is an accurate way to identify complicated plaque. MRDTI focuses on signs of bleeding within a plaque. Complicated plaque appears as a bright (high) MRI signal on the resulting image.

The study involved 63 patients who had surgery to treat obstructions in carotid arteries. Pathology studies of the plaque removed during surgery showed that 44 specimens met criteria for complicated plaque. MRDTI performed before surgery missed the complicated plaque in only three of the 44 cases, resulting in a positive predictive accuracy of 93 percent. The ability of two researchers to identify the same MRDTI abnormalities was very high; so they concluded that MRDTI is well suited to evaluate carotid disease.

In the second study, Moody and lead author Rachel E. Murphy, M.D. of University Hospital in Nottingham, U.K., evaluated MRI’s ability to determine how often complicated plaque occurs in the carotid (neck) arteries of patients who have symptoms that suggest impending stroke.

They studied 120 symptomatic patients and 28 arteries in 14 age-matched people (controls) who had no prior evidence of carotid disease.

Of the 72 people in the symptomatic group, 33 patients had high signal in both carotid arteries and 39 had high signal only in the artery on the side associated with the symptoms. Thirty-six percent of asymptomatic arteries on the opposite side of the neck contained high signal. The researchers note this finding provides evidence of asymptomatic high-risk disease and thus provides the opportunity to detect at-risk patients. The researchers plan further investigations.

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Other co-authors of the two studies are Paul S. Morgan, Ph.D.; Ann L. Martel, Ph.D.; G. S. Delay, D.C.R; Steve Allder, M.D.; Shane T. MacSweeney, M.D.; William G. Tennant, M.D.; John Gladman, M.D.; John Lowe, M.D. and Beverley J. Hunt M.D.

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