ELECTROCARDIOGRAPHIC FINDINGS OF HEART-RATE AND CONDUCTION TIMES IN ATHLETIC STUDENTS AND SEDENTARY CONTROL SUBJECTS

We have investigated resting electrocardiograms in 1,299 athletic students and 151 sedentary control subjects. Bradycardia was significantly more common in athletes. The athletic group was divided according to a heart rate <50, 50-100, and above 100 beats/min. Atrioventricular conduction time, prevalence of ectopic beats and other rhythms, parameters of right and left ventricular hypertrophy, ST elevation, and T wave amplitude were increased in the sinus bradycardia group. A significant negative correlation was found between heart rate and PQ duration in athletes. In the sinus tachycardia group, the PQ duration was shorter and the ST depression more prominent than in the other groups. The subjects were also divided according to PQ greater than or equal to 0.22, 0.21-0.12, and <0.12 s. Parameters of left ventricular hypertrophy were markedly increased in athletes with PQ greater than or equal to 0.22 s, while the heart rate was only slightly decreased, suggesting an association between prolonged atrioventricular conduction time and left ventricular hypertrophy. Incomplete right bundle branch block was associated with a lower heart rate, increased duration of QRS and QT(c), voltage of precordial Q waves, indices of right ventricular hypertrophy, and negative T waves. These findings are typical of right ventricular hypertrophy, indicating a close relation of incomplete right bundle branch block to right ventricular hypertrophy.