Normal limits of the electrocardiogram in a Chinese population.

12-lead electrocardiograms (ECGs) from 503 healthy Chinese individuals were computer-analyzed to derive the normal limits of the ECG in a Chinese population. With respect to ECG amplitudes, there were highly significant differences between men and women. The mean S wave amplitude in V2 decreased with increasing age, but the mean R wave amplitude in V5, for example, remained remarkably constant throughout the age groups. The QRS duration was on average 7.6 msec shorter in women than in men. The mean frontal QRS axis shifted superiorly by 17 degrees with increasing age, resulting in an upward trend in R wave amplitude in leads I and aVL. It was concluded that ECG diagnostic criteria for Chinese individuals should be age- and sex-dependent.