This distinction has significant clinical implications, the researchers said. While enlargement of the heart can be a natural and beneficial response to exercise training, it can also be an early warning sign for such harmful conditions as heart failure.

These findings, based on a series of experiments in mice, could help settle a long-running controversy among cardiologists concerning heart enlargement, or cardiac hypertrophy, according to Duke cardiologist Howard Rockman, M.D., who led the team of Duke and University of North Carolina-Chapel Hill researchers.

The researchers published their findings on June, 1, 2006, in the Journal of Clinical Investigation. The study was supported by the National Institutes of Health.

"If you look at the hearts of athletes, they are larger than normal," Rockman said. "On the other hand, patients with high blood pressure also tend have larger-than-normal hearts. So why are some cardiac overloads, such as exercise, good for the heart, while others, such as high blood pressure, not?"

In athletes, the heart's pumping chambers enlarge to compensate for the body's increased demand for oxygen-rich blood. But in patients with heart failure, the heart walls themselves become thicker, heavier and less efficient in pumping blood.

"For more than a century there has been intense debate over why some stresses or overloads on the heart are beneficial and others lead to disease," Rockman continued. "The prevailing wisdom was that since exercise is an intermittent event and high blood pressure is a chronic condition, the duration of the cardiac stress was key. However, our studies appear to d
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Contact: Richard Merritt
Merri006@mc.duke.edu
919-684-4148
Duke University Medical Center
1-Jun-2006