The Course of Left Ventricular Potentials in the First 15 Months of Life. ECG Findings Based on Follow-up of Normal Newborns

Follow-up of 56 newborns showed that, R amplitudes in V5 and V6 increased during infancy as a 2nd degree polynomial. The increase in left potentials in the first two months was significant when the age-dependent voltage factor derived from the standard leads was held constant. There was a synchronous decrease in the S amplitude which resulted from increasing rightward and posterior orientation of the late QRS-vector loop in the horizontal plane. The correlations, between amplitudes of left precordial R waves and right precordial S waves in different age groups were not significant, but they showed very high correlations between them selves. The upper normal limit of R in V5 increased from 17mm in newborns to 32-34 mm after the age of 4 months. Corresponding values in V6 were lower, i.e., 8 and 25 mm. A left precordial rS pattern in newborns, was not observed after the second month. Adult type of QRS pattern started to be observed after 9 months in only 4 % and at 15 months in 12 %. The incidence of left precordial Q-wave was 10 % in newborns, and increased later. Upper voltage limit for depth of Q in V5 was 3 mm in newborns, 5 mm at 2 months and 6 mm at 15 months. These data aid in a better delineation of pathologic states in this early phase of life.