E. Henriksen et al., AN ECHOCARDIOGRAPHIC STUDY COMPARING MALE SWEDISH ELITE ORIENTEERS WITH OTHER ELITE ENDURANCE ATHLETES, The American journal of cardiology, 79(4), 1997, pp. 521
Between 1979 and 1992, there were 16 known cases of sudden unexpected
cardiac death among young Swedish orienteers, whose autopsies showed m
yocarditis to be a common finding. Therefore, 96 elite orienteers and
47 controls underwent echocardiography, showing left ventricular wall
motion abnormalities in 9% of the orienteers compared with 4% in the c
ontrols.