[Signal-averaged electrocardiograms in young athletes--sudden death during exercise]

Our objective was to evaluate the incidence of abnormal SAECG in young athletes, and to evaluate the relationship between abnormal SAECG and electrocardiographic and echocardiographic parameters. The presence of an abnormal SAECG was evaluated in 796 athletes (mean age 19 years), and its relation to findings on 12-lead electro-cardiograms, echocardiograms, and arrhythmias was studied, as recorded by the Holter monitor. An abnormal SAECG was defined as two of the three following criteria: filtered QRS duration > or = 114 msec, root mean squared voltage in the terminal 40 msec < or = 20 microV, or duration < 40 microV > or = 38 msec. Abnormal SAECGs were present in 68 (8.5%) of the athletes and were associated with a smaller left ventricular mass. Athletes who performed anaerobic exercise tended to exhibit a high incidence of abnormal SAECG, which was associated with smaller left ventricular mass. No serious ventricular arrhythmias were observed on Holter monitoring for 24h and during a follow-up period of 20 +/- 10 months in 796 subjects. Continuous anaerobic exercise may induce abnormal SAECG due to the development of delayed myocardial conduction or to electrical inhomogeneity in the cardiac tissue. The presence of an abnormal SAECG was unrelated to the development of arrhythmias in young athletes.