From the floor of the annual meeting of the American Heart Association

Effects of fibrosis during exercise stress to be studied further

NEW ORLEANS | Canadian researchers are using imaging technology to gain new insights into athletes’ hearts—and the factors that might put them at increased risk for sudden cardiac death.

In her paper presentation, Myra Cocker, a PhD candidate at the Stephenson Cardiovascular MR Centre in Calgary, showed that elite endurance athletes have more myocardial injury and larger ventricles than people who engage only in light recreational activity.

She and her colleagues recruited 48 Olympic-calibre athletes, mean age 32 years, from sports such as swimming, speed skating, cross-country skiing and marathon running, as well as eight healthy controls, mean age 31.

Contrast-enhanced cardiovascular magnetic resonance scans revealed that 36 athletes (75%) had non-ischemic myocardial fibrosis, compared with only one control (13%).

The mean extent of the fibrosis in the athletes’ hearts was 10.7%.

Ventricular dysfunction
Measures of left ventricular dysfunction, including left-ventricular end-diastolic, end-systolic and stroke volumes were similar in the controls and the athletes without fibrosis, but were significantly elevated in the athletes with fibrosis (see chart). However, there was no difference in ejection fraction.

“There’s very little effect of myocardial fibrosis on function, but we were studying these athletes during rest, so we don’t know what the effect of myocardial fibrosis is at stress, which is something that we’re going to evaluate further,” Cocker said.

Possible mechanisms that could lead to the myocardial fibrosis include repetitive exposure to increased physical stress levels (troponin levels, for example, have been shown to be elevated after competitive events) and exercising during systemic viral infections such as influenza.

Dr. Matthias Friedrich, the senior study author and director of the Stephenson Cardiovascular MR Centre, told the Medical Post it’s too early to say whether the presence of myocardial fibrosis has any prognostic implications for these athletes, such as predisposing them toward arrhythmias. It may be that it simply limits their maximum capacity, preventing them from becoming world champions regardless of how hard they train.