University of Iowa Health Science Relations and
Richard Kerber, MD
Professor of Internal Medicine
First Published: November 2000
Last Revised: January 2004
Peer Review Status: Internally Peer Reviewed

It's a case of having too much heart. That's the simple explanation for one of medicine's more complex problems--sudden death among athletes.

The heart disorder, called hypertrophic cardiomyopathy, is an abnormal thickening of the muscles in the walls of the heart. It causes half of the sudden death cases involving athletes under age 35.

"The heart is primarily made of muscle and can contract an average of 60 to 100 times a minute," says Dr. Richard Kerber, professor of internal medicine at the University of Iowa College of Medicine. "Under normal conditions, the heart conforms to a certain size and thickness. In hypertrophic cardiomyopathy, the heart muscle becomes overgrown and the walls of the heart are abnormally thick." A thickening of the heart's walls can lead to an abnormal heart rhythm that can cause sudden and unexpected death in athletes, he notes.

The disease is difficult to detect. In fact, an athlete can train for years before symptoms appear.

"In a majority of cases, hypertrophic cardiomyopathy is inherited and develops over time, typically in the late teenage years," Kerber says. Symptoms include black-out spells, unexplained dizziness, and chest pains that occur briefly during competition or training, but then disappear with rest.

If a physician suspects hypertrophic cardiomyopathy, an echocardiogram confirms the diagnosis. By using ultrasound (sound or sonar waves), this test provides a two-dimensional image of the heart.

Although no cure for the disease exists, in some cases pacemakers can improve the condition. People with hypertrophic cardiomyopathy can lead normal lives. Symptoms can be regulated with medications, Kerber says. An enlarged heart doesn't always mean a person has hypertrophic cardiomyopathy, Kerber adds. "In serious competitive athletes, particularly those in endurance sports such as distance running, cycling, and swimming, the heart will enlarge on its own."

Commonly referred to as "athlete's heart" this increase in size is nature's way of adapting the heart to endurance exercises. "Unlike hypertrophic cardiomyopathy, this is a normal adaptation, not a disease," Kerber says.

If you have questions about hypertrophic cardiomyopathy, talk with your physician.