Male triathletes may be risking their hearts

Competitive male triathletes face a higher risk of a potentially harmful heart condition called myocardial fibrosis, according to resent research

In the study being presented at the annual meeting of the Radiological Society of North America (RSNA), the increased risk, which was not evident in female triathletes, was directly associated with the athletes' amount of exercise.

Myocardial fibrosis is scarring of the heart. It usually affects the pumping chambers, also known as the ventricles. The condition might progress to heart failure. While regular exercise has beneficial effects on the cardiovascular system, previous studies have shown the presence of myocardial fibrosis in elite athletes.

"The clinical relevance of these scars is currently unclear," said lead author Jitka Starekova from the University Medical Center Hamburg-Eppendorf in Hamburg, Germany. "However, they might be a foundation for future heart failure and arrhythmia."

Starekova and colleagues recently studied a group of triathletes, including 55 men, average age 44, and 30 women, average age 43. The study group underwent cardiac MRI exams with the contrast agent gadolinium, which is taken up by both normal and injured heart muscle tissue.

Gadolinium washes out quickly in normal heart tissue, but much more slowly in scarred tissue, revealing a difference in contrast between normal and injured heart muscle after approximately 10 minutes. This phenomenon, known as late gadolinium enhancement, is a useful tool for detection of myocardial fibrosis.

Evidence of myocardial fibrosis was apparent in the left ventricle -- the heart's main pumping chamber -- in 10 of 55 of the men, or 18 percent, but in none of the women.

These same athletes had completed significantly longer total, swimming and cycling distances and had higher peak exercise systolic blood pressure than their counterparts without myocardial fibrosis.

Lifetime competition history for the athletes showed that the number of completed Iron Man triathlons and the number of middle distance triathlons were significantly higher in the male triathlete population compared to the female triathlete population, suggesting that the fibrosis risk was likely associated with exercise level.

There are several possible factors for the link between the amount of exercise and the risk of myocardial fibrosis, according to Dr. Starekova. Higher exercise-induced systolic blood pressure may result in greater myocardial mass, she said, and more exercise might expose the athlete to a higher risk of myocarditis, or inflammation of the heart muscle. These factors, in combination with repeatedly increased stress of the left ventricular wall due to exercise, could injure the heart muscle.

Other factors may be responsible for the striking difference in myocardial fibrosis risk between male and female triathletes, Starekova said, including the presence of testosterone.

The researchers plan long-term follow-up studies to see if any cardiac events occur in the triathletes who had evidence of myocardial fibrosis.