May 22, 2000 -- Last Friday, Jose Armstrong had a magnetic resonance imaging test (MRI) for heart disease. He lay in a narrow chamber for about an hour, bombarded by FM radio waves, while his doctors observed the blood flow through his heart, giving him occasional instructions though earphones.
Later the same day, Armstrong had an angiogram -- another, much more common way to evaluate the heart. His doctors injected a local anesthetic into his groin, inserted very thin tubing into an artery, and pushed it upward until it entered blood vessels in his heart. A dye was injected into the tube, and X-rays allowed his doctors to see whether the arteries in his heart were blocked.
Both of these tests are somewhat unusual experiences, Armstrong says. "The MRI can be intimidating, because you lie in a narrow, enclosed space. But fortunately I'm not claustrophobic. During the angiogram, you feel a rush of heat when they release the dye into your artery." Most importantly, Armstrong adds, "the angiogram is an intrusion into your body, while the MRI gives your doctors a picture of your heart without any intrusion." Armstrong, 65, lives in Ponce, Puerto Rico. He was visiting his daughter in New York City when he developed chest pain and went to Mt. Sinai Medical Center for treatment.
"The angiogram is the currently accepted diagnostic tool for coronary artery blockages," says Zahi Fayad, PhD, who has been studying MRIs and heart disease for 10 years. "We also did an MRI on Mr. Armstrong as part of our ongoing research, so we can compare the results of the two tests." Fayad is assistant professor of medicine at Mt. Sinai School of Medicine in New York City and director of cardiovascular imaging at Mount Sinai Medical Center.
A just-released study says MRI can be an effective way to evaluate patients after they have had an angioplasty -- which is a procedure to open blocked heart arteries. About 500,000 people have angioplasties each year. During this procedure, a tiny balloon is inserted into closed heart arteries and inflated to open them back up. Unfortunately, in about a third of cases, the arteries close back up within six months. Currently, the angiogram is the accepted test to see whether this has happened. However, because it involves threading a fine tube into the heart, it carries some risks.
"We've developed a rapid, noninvasive, low-risk way to find out, if you've had an angioplasty, whether your arteries have blocked up again," says W. Gregory Hundley, MD, lead author of the study. "You don't have to have an angiogram, and the result is equivalent." Hundley is assistant professor of internal medicine (cardiology) and radiology at Wake Forest University Baptist Medical Center in Winston-Salem, N.C.
Hundley believes that MRI has many advantages over angiography: it is noninvasive, it doesn't use ionizing radiation, and it is quicker. Direct costs for an angiogram would be about $3,000, he estimates, compared to $200 to $300 for an MRI. "This sort of work can be performed [with] hardware that's widely available," he says.
"The Wake Forest research is in line with what we've been seeing in other studies of MRI and the heart," says Fayad. "Little by little, studies have been showing that MRI is effective in detecting coronary artery blockages. In the future, it will complement the tools we already use to assess cardiovascular disease."
However, Thomas Davis, MD, an independent observer, is far more cautious about the potential usefulness of MRI. "The Wake Forest study only looked at 17 patients. MRI may in fact turn out to be the cat's meow, but we don't have sufficient convincing data yet to start using it. First, I'd want to see studies on thousands of patients, all kinds of patients." Davis is medical director of the cardiac intensive care unit and cardiovascular center at St. John Hospital in Detroit.
Fayad believes successful use of MRI depends on physicians' degree of experience and effort, and how aggressive they are in their research. "Some people don't know how to use this method yet, but in experienced hands, we think it does pretty well." However, he agrees that much larger studies are needed. "The jury is still out," he says.
This research was funded by the National Institutes of Health, the American Heart Association North Carolina affiliate, and the North Carolina Baptist Medical Center Technology Development Fund.
- Patients who have a blocked coronary artery usually undergo angioplasty, where a balloon is inflated inside the artery to open it back up. Often, however, the artery closes back up again.
- New research shows that an MRI may be able to detect just as well as an angiogram whether or not the artery has closed up again.
- MRI is noninvasive and is easier to perform than an angiogram, which involves inserting a tube through the groin up to the heart.