June 23, 1999 DALLAS, June 22 -- A simple 30-minute test may soon be a safer and more convenient way to diagnose coronary heart disease, the cause of heart attacks, than the widely used invasive technique of X-ray angiography, researchers report today in Circulation: Journal of the American Heart Association.
Called three-dimensional (3-D) coronary magnetic resonance angiography (MRA), the test uses powerful magnets to provide images of the coronary arteries, the blood vessels of the heart. Unlike conventional coronary angiography, the test does not require injection of a dye or exposure to X-ray. Thus, it causes considerably less discomfort and risk for the patient and is also less costly.
During conventional coronary angiography, an X-ray examination of the blood vessels is performed to look for blockages that obstruct blood flow to the heart, thereby triggering a heart attack. During conventional angiography, patients must lie still while a small tube is placed inside the blood vessels to deliver the dye. After X-rays are taken of the blood vessels, the patient often remains in the hospital for a recovery period of four to six hours.
The procedure creates a risk of infection and bleeding, and in a small fraction of cases, heart attack and stroke, says Warren J. Manning, M.D., co-director of the Cardiac MRA Center at Beth Israel Deaconess Medical Center in Boston and senior author of the study.
"We have multiple methods to try to determine if our patients have coronary heart disease," says Manning. "However, we have no methods to image the coronary arteries themselves that do not require injecting a dye into a blood vessel."
Manning and his research colleagues used a sophisticated MRA approach to enhance the MRA image quality and spatial resolution to provide detailed images of the blood vessels.
With the new MRA technique, two sets of images are acquired: one for the blood vessels on the left side of the heart and one for the right side, with each set of images taking 10 to 15 minutes. Patients simply need to lie still and breathe normally.
"So, in essence, in about a half an hour, you're done. It is likely that the technique will become the standard approach at many cardiac MRA centers because of its ease of use and high quality," says Manning, associate professor of medicine and radiology at Harvard Medical School.
A 20- to 30-minute 3-D MRA imaging session is also less than one-quarter of the cost of an X-ray angiogram, Manning says.
Individuals who are found to have blockages in their blood vessels can then be treated with angioplasty or surgery. If untreated, the blockages can lead to a heart attack or worsening chest pain.
The team first reported that MRA could be used for coronary artery imaging in 1993, Manning says, but the approach at that time required patients to hold their breath 30 to 40 times for about 16 to 20 seconds each time.
Even though most patients could be trained to do this, the clarity of the images was not sufficient, he says. With the new MRA methods, patients no longer need to hold their breath and image quality is improved.
In the study led by Rene' M. Botnar, Ph.D., clinical scientist at the Cardiac MRA Center of the Beth Israel Deaconess Medical Center, eight healthy adults and five patients with confirmed heart disease underwent the new technique.
The team reported that it allows for improved definition of the heart's arteries and MRA compared well with conventional X-ray angiograms.
The team has initiated a study to examine the accuracy of this MRA technique compared to X-ray angiography at eight medical centers around the world, says Manning.
Another advantage of the MRA technique is that it also can be used to evaluate the anatomy, contractility, perfusion and valvular function of the heart, thereby providing a comprehensive, non-invasive, cardiac examination. Co-authors were Matthias Stuber, Ph.D.; Peter G. Danias, M.D., Ph.D. and Kraig V. Kissinger, B.S., R.T.
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