A new study using advanced cardiac imaging technology indicates that cardiac abnormalities experienced by some marathon runners following competition are temporary, and do not result in damage to the heart muscle. The study, conducted by researchers at the University of Manitoba, marked the first use of cardiac magnetic resonance imaging, or CMR, in a post-marathon setting.
The research will be presented on May 17, at the 105th International Conference of the American Thoracic Society in San Diego.
"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," said study investigator Davinder S. Jassal, M.D., assistant professor of cardiology, radiology and physiology at St. Boniface General Hospital Research Centre in Winnipeg.
The study examined the cardiac health of 14 runners who participated in the full 2008 Manitoba Marathon in Winnipeg, Canada. All runners were classified, for purposes of the study, as "non-elite," meaning they participated on a casual, non-professional basis, with limited or no training. Prior to the marathon, each study participant underwent a comprehensive health screening, including blood tests to determine the levels of cardiac biomarkers, factors present in the blood that reflect the health of the heart muscle. Following the race, additional blood samples were taken and echocardiograms and CMR were performed.
Earlier studies have confirmed that cardiac biomarkers are elevated in many casual, non-professional athletes following competition, indicating possible damage to the heart muscle. In this study, echocardiograms and CMR performed immediately after competition revealed abnormalities, including irregularities in diastolic filling (relaxation abnormalities) on both sides of the heart and a decrease from 64 percent to 43 percent in the pumping function of the right ventricle. Although the cardiac biomarkers were elevated post marathon, there was no evidence of direct permanent injury to the heart muscle on CMR imaging.
"By using CMR, we were able to definitively show that these fluctuations do not result in any true damage of the heart, and the right ventricular dysfunction is transient, recovering one week following the race," Dr. Jassal noted.
The researchers are planning 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.
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