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NEW MRI CAN DEMONSTRATE CORONARY ARTERY PLAQUE THAT CAUSES 70 PERCENT OF ALL HEART ATTACKS
CHICAGO -- An adaptation to magnetic resonance imaging (MRI) that can noninvasively show "soft" plaque in the coronary arteries may have far-reaching ramifications for identifying people at high risk of heart attack, according to preliminary research being presented here today at the 85th Scientific Assembly and Annual Meeting of the Radiological Society of North America (RSNA).
"In 70 percent of people who have heart attacks, the cause is 'vulnerable plaque,' which is soft and is more likely to rupture than hard, stable plaque," said Zahi A. Fayad, Ph.D., assistant professor of radiology and director of cardiovascular imaging, physics and research at Mt. Sinai School of Medicine, New York. Dr. Fayad and his team developed a modification of MRI that can clearly look inside the coronary arteries. "This could change the face of cardiology imaging. The only other technology that can actually look at the type of plaque on the walls of the arteries is intravascular ultrasound (IVUS), which is invasive, and the pictures are not nearly as good."
Heart disease is the leading cause of mortality in the United States. As many as 1.5 million Americans will have a new or recurrent heart attack this year, and about a third of them will die, according to the American Heart Association.
In the Mt. Sinai study, 13 subjects underwent MRI: 8 healthy subjects and 5 who had been determined by X-ray angiography to have heart disease. The study specifically looked at 5 arteries in each of the latter group that had blockage of 40 percent or more. Preliminary findings showed that plaque build-up in the heart patients was 2 to 10 times thicker than in the healthy subjects, and that the plaque bulged in some places, indicating the more dangerous, vulnerable plaque. The study showed that it is possible to visualize the shape of the plaque inside the arteries, and that even though blood flow may be adequate in arteries with plaque buildup, having vulnerable plaques puts patients at risk for heart attack, and should be treated.
In the last decade, researchers have found that some plaques are more vulnerable to breaking off from the walls of the artery and prompting a blood clot, which travels to the heart and can cause heart attack. This so-called vulnerable plaque is soft because of its high lipid, or fat, content.
Treatment includes life-style changes, such as diet and exercise; the new lipid-lowering drugs; angioplasty and coronary bypass surgery. It's unclear why certain people may be more prone to developing vulnerable plaques, but it's believed to be related to a number of factors, including diet and genetics. Smoking, hypertension, high cholesterol and diabetes are believed to injure the artery walls, causing plaque to build up. Some plaques become harder and less risky, while other plaques apparently stay soft because there is too much of a cholesterol build- up, said Dr. Fayad.
"MRI also might be used to see if treatment is working, and to help determine whether other measures need to be taken," said Dr. Fayad. "It also may tell us when the plaque is stable, and that perhaps in some cases, no therapy is needed."
MRI uses no radiation, creating images based on the water content and chemical composition of the structures within the body. The MRI in this study involves using an enhanced cardiovascular magnet found at most heart centers and teaching hospitals. The enhanced MRI is fast enough to image a beating heart.
Co-authors of a paper on the topic being presented by Dr. Fayad are: Valentin Fuster, M.D., Ph.D.; John T. Fallon, M.D., Ph.D.; and Samin Sharma, M.D.
The RSNA is an association of 31,000 radiologists and physicists in medicine dedicated to education and research in the science of radiology. The Society's headquarters are located at 820 Jorie Blvd., Oak Brook, Illinois 60523-2251.
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Note: Copies of 1999 RSNA news releases are available online at http://www.pcipr.com/rsna beginning Monday, Nov. 29.
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