Thallium-201 Myocardial Imaging at Rest in Male Orienteers and Other Endurance Athletes

During the period 1979 to 1992, 16 sudden unexpected cardiac deaths were known to have occurred in young Swedish orienteers. Autopsy indicated myocarditis to be the most frequent finding, most often combined with extensive myocardial fibrosis. The aim of the present investigation was to explore whether young male orienteers show a higher frequency than other young elite endurance athletes (controls) in the occurrence of Thallium-201 myocardial perfusion defects at rest, suggestive of fibrosis evoked by myocarditis. Thallium-201 perfusion abnormalities at rest were more frequently found in the controls than in the orienteers (26% vs. 12%, p=0.03). Uneven Tl-201 perfusion was associated with left ventricular mass (r=0.32, r=0.24, p<0.01, p=0.02) and body weight (r=0.30, r=0.31, p<0.01, p=0.03) in orienteers and controls, respectively. Echocardiographic left ventricular wall motion abnormalities were found in 11 athletes (9 orienteers and 2 controls) but only two displayed an abnormal Thallium-201 perfusion scan at rest. Perfusion abnormalities at rest did not occur more frequently in the orienteers but were commonly found in both groups of apparently healthy athletes making it futile to discern abnormals from normals. Thallium-201 perfusion aberrations were not associated with left ventricular wall motion abnormalities obtained by echocardiography.