Oct. 14, 1999 WINSTON-SALEM, N.C. -- Researchers at Wake Forest University Baptist Medical Center are the first in the world to report success using magnetic resonance imaging (MRI) to view the heart during vigorous beating and to diagnose blocked arteries based on an abnormal pumping motion.
The new test was made possible by speeding up the MRI scanner and creating new software that allows for imaging that is very close to "real-time." Doctors can see heart movement within seconds after it happens. Previously, it took an average of five minutes to see the images.
The researchers say this is an important step toward using MRI as a screening and diagnostic tool for heart disease.
"A lot of new doors have been opened with this technology," said Greg Hundley, M.D., assistant professor of cardiology and radiology and leader of the Medical Center's MRI research team.
In the current issue of Circulation, a journal of the American Heart Association, the researchers report using the new test as an alternative for patients unable to have an ultrasound test to image the heart. Ultrasound is currently the most common non-invasive test for detecting heart disease. About 10-20 percent of people, however, cannot have the ultrasound test because they are obese or have health conditions, such as emphysema, that interfere with getting a clear image of the heart.
"MRI gives you a non-invasive alternative for people who cannot have an ultrasound, who are often our sickest patients," said Hundley.
More than 350 Medical Center patients have had the MRI test, which researchers said is just as accurate as ultrasound at diagnosing blocked arteries. Patients spend about 35 minutes in the MRI scanner.
Craig Hamilton, Ph.D., assistant professor of radiology, developed the software that allows the researchers to see the heart's action almost immediately.
"This faster imaging and visualization is what makes it possible to do a stress test with MRI," said Hundley.
With both ultrasound and MRI, the aim is to view the heart during vigorous pumping. Patients are given drugs to speed up their hearts so they beat at close to capacity. Normally, both sides of the heart contract with equal force. If the imaging tests show that one side of the heart wall doesn't contract normally, doctors know it isn't getting enough oxygen due to blocked blood vessels.
Because MRI can evaluate many parts of the body, the test could be useful for patients with multiple symptoms. A patient could be tested for blood vessel disease in the coronary arteries and in the legs at one time, for example.
In June, the MRI researchers reported another breakthrough in MRI imaging. They were first in the world to report the successful use of MRI to visualize blockages and measure blood flow in vessels leading to the heart. With colleagues from the University of Texas Southwestern Medical Center, they reported that in a study of 30 patients who had both MRI scanning and cardiac catheterization, the MRI was just as effective as cardiac catheterization at diagnosing significant blockages in the two main arteries of the heart.
"MRI allows us not only to locate a blockage, but to determine whether it limits blood flow enough to warrant treatment," said Hundley. "With further development, many patients may benefit from this approach to assessing coronary blockages."
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