Evolution of QRS and ST-T-wave body surface potential distributions during the first year of life.

Using a system for obtaining body surface potential distributions from 150 sites on the anterior and posterior torso, 43 body surface maps were evaluated in 31 normal infants, ages 15 hours to 10 months. Serial maps were obtained at 0.6-msec intervals during QRS and at 2.4-4-msec intervals throughout the ST-T wave. We found an orderly evolution of both QRS and ST-T wave maps during the first year of life. In the newborn, the patterns during the latter half of QRS were consistent with early completion of depolarization of the left ventricle and prolonged depolarization of the right ventricle. The patterns changed gradually such that by 5-6 months of age, the maps demonstrated simultaneous effects of both right and left ventricles during the latter half of QRS. By 9 months, the QRS patterns were similar to those of older children and adults. The changes in the ST-T-wave maps were consistent with the idea that age-related changes in the sequence of ventricular activation.