MRI May Identify Those At High Risk For Heart Attacks, Strokes

November 12, 1996

A rapid nuclear magnetic resonance imaging (MRI) test can measure heart cell damage from heart attacks in living animals, according to studies at Johns Hopkins and Northwestern University.

The results put researchers another step closer to developing the technique for use in people to improve diagnosis and treatment of heart attacks, say the researchers. The study, which was supported by the National Institutes of Health, will be presented at 10:30 a.m., Nov. 13 at the American Heart Association's 69th annual Scientific Sessions in New Orleans.

The new method, first shown to work on animal heart cells and now on beating animal hearts, quickly measures damage to the heart when blood flow stops and restarts as in a heart attack. The technique, which reduces MRI times from four hours to seven minutes, produces sodium "maps" of the heart, showing dead cells as brighter and living cells as darker. In a heart attack, sodium accumulates in dead heart cells. Unlike echocardiography and stress tests, which are indirect measurements, the new MRI method directly measures the extent of damage to heart cells.

"We're near to creating a technique to rapidly image the naturally occurring sodium nucleus in cardiac cells in humans," says Joao A. C. Lima, M.D., a study co-author and an assistant professor of medicine. "An important question is what parts of the heart are alive, damaged or dead after a heart attack, and this could be an excellent method to determine which areas are viable."

In a study last year using rabbit heart cells, Hopkins scientists developed the rapid MRI method to detect the high sodium concentrations that accumulate in heart cells killed when blood flow stops and restarts, thus measuring how much heart tissue had died.

Results of the new study, using rabbits and dogs, show the technique also works in live small and large animals before and during blockage of blood flow in coronary arteries and after blood flow restarts. This information can be used to assess quickly a heart attack's damage and guide drug and surgical treatment such as angioplasty, the researchers say.

"This technique may help explain not only the anatomy of the dead tissue but also how well the cell membrane is functioning," says Lima.

Results of the sodium MRI study were confirmed in another Hopkins and Northwestern animal study using standard contrast-enhanced MRI, which generates maps of heart tissue based on hydrogen atoms.

The studies' other authors were Raymond J. Kim, M.D., and Enn-Ling Chen, M.D., of Hopkins and Robert M. Judd, M.D., and Francis J. Klocke, M.D., of Northwestern.

--JHMI--

Johns Hopkins Medicine

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