Hypertrophy of the heart; electrocardiographic distinction between physiologic and pathologic enlargement.

Electrocardiograms of marathon runners were examined to study hypertrophy of the heart due to prolonged physical exertion and to differentiate this from hypertrophy due to various disease states, especially essential hypertension, aortic valvular disease and coarctation of the aorta. The electrocardiogram of the marathon runners was characterized by a slow cardiac rate, high voltage of the QRS complexes and T waves in the standard and/or precordial leads with normal R/T ratios. There was moderate enlargement of the heart as observed on teleoroentgenogram. These findings are characteristic of physiologic hypertrophy of the heart and should be suspected among patients having a history of athletics calling for endurance. Immediately after running, all waves showed an increased voltage and the heart size decreased. The concept of the secondary T wave in hypertension as a part of the left ventricular strain pattern was challenged by the observation that the increased voltage of the R waves in lead V5 and other leads seen in marathon runners and in certain patients with hypertension, aortic stenosis, aortic insufficiency and coarctation of the aorta were not necessarily associated with typical discordant S-T segments and T waves. There was a higher incidence of dyspnea, angina pectoris and cardiac enlargement among hypertensive patients with discordant T waves than among hypertensive patients without these changes. Thus it is felt that the discordant waves are primary and are not merely secondary to the increased area of the R waves. Primary T waves suggest myocardial disease, possibly anoxia of the subendocardium.