-- An adaptation to MRI noninvasively enables radiologists to distinguish
between a type of plaque in the coronary arteries that is likely to
cause a heart attack and plaque that isn't.
-- There is hard, more stable plaque and soft 'vulnerable' plaque, which
causes 70 percent of heart attacks.
-- Heart disease is the leading cause of mortality in the United States.
As many as 1.5 million Americans will have a heart attack this year,
and about one-third of them will die.
CHICAGO, Dec. 3 /PRNewswire/ -- 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 cardiac 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.
Note: Copies of 1999 RSNA news releases are available online at
http://www.pcipr.com/rsna.
SOURCE The Radiological Society of North America
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