The clinical features of athletic hearts are confusing to physicians who are unfamiliar with them. In particular, the diagnosis of hypertrophic cardiomyopathy may be suggested. The clinical signs of athletes' hearts are discussed with special reference to this difficult diagnosis. Emphasis is placed on the results of special investigations including the electrocardiogram and echocardiogram. The changes seen in athletic hearts are physiologic adaptations that do not appear to cause significant problems. Long-term follow up of the more extreme examples, however, is very limited, and this is an area where further information is needed. Resting bradycardia is a common feature in athletes, but abnormal tachyarrhythmias on exertion signify cardiac disease and are not a part of the athlete heart syndrome.
