EVALUATION OF ABNORMAL SIGNAL-AVERAGED ELECTROCARDIOGRAMS IN YOUNG ATHLETES

Our objectives in this study were to determine the incidence of abnorm al signal-averaged ECG (SAECG) and its relation to the extent and type of exercise in young healthy athletes, and to evaluate the associatio n, if any, between the development of abnormal SAECGs and vigorous exe rcise. The presence of an abnormal SAECG was evaluated in 796 athletes (mean age 19 years), and its relation to findings on 12-lead electroc ardiogram, echocardiogram, and the presence arrhythmias was studied us ing Holter monitoring. An SAECG was considered abnormal when any one o f the three following criteria was met: filtered QRS duration of more than 114 msec, root-mean-square voltage in the terminal 40 msec of les s than 20 mu V, or a voltage of less than 40 mu V for more than 38 mse c. Abnormal SAECGs were present in 68 (8.5%) of the athletes and were associated with a smaller left ventricular mass. Athletes who performe d anaerobic exercise tended to exhibit a high incidence of abnormal SA ECGs, which was associated with a smaller left ventricular mass. No se rious ventricular arrhythmias were observed on 24h Holter monitoring o r during the follow-up period of 20 +/- 10 months. There were no sudde n cardiac deaths. Continuous anaerobic exercise may induce abnormal SA ECGs through the development of delayed myocardial conduction or elect rical inhomogeneity in cardiac tissue. The presence of an abnormal SAE CG was unrelated to the development of arrhythmias in young athletes.