Marathon runners earn clean bills of heart health with MRI

Myocardial anomalies detected in long-distance runners after they cross the finish line should not be interpreted as signs of possible heart damage. Using cardiac MR, Canadian investigators have found evidence that these abnormalities are only temporary.

"By using CMR, we were able to definitively show that these fluctuations do not result in any true damage of the heart. The right ventricular dysfunction is transient, recovering one week following the race," said study investigator Dr. Davinder S. Jassal, an assistant professor of cardiology, radiology, and physiology at St. Boniface General Hospital Research Center in Winnipeg, MB.

Jassal and colleagues assessed the cardiac health of 14 nonprofessional athletes who ran the 2008 Manitoba Marathon hosted in Winnipeg. All subjects underwent a comprehensive health screening before the marathon, including a blood test of cardiac biomarkers to evaluate myocardial health. They also underwent additional blood tests, echocardiograms, and CMR after the race.  

Results from the echocardiograms and CMR scans performed immediately after the marathon showed diastolic filling irregularities on both sides of the heart and a decrease from 64% to 43% in the pumping function of the right ventricle. Cardiac biomarkers also showed postmarathon abnormalities.

The investigators found no evidence, however, of permanent myocardial injury on follow-up CMR. They presented results in May at the 2009 International Conference of the American Thoracic Society in San Diego.

More nonprofessional athletes are running marathons for pleasure and the promise of improved cardiovascular health. But until this study, clinical experience suggested extreme long-distance running could be a killer in more than one sense.

"Although previous studies of marathon runners have demonstrated biochemical evidence of cardiac injury and have correlated these findings with echocardiographic evidence of cardiac dysfunction, this was the first time CMR has been used to further evaluate and understand the effects of marathon running on the heart," Jassal said.

Jassal's investigative group plans additional studies to determine whether these abnormalities may result in permanent damage in runners who participate in more than one marathon during a 12-month period.