The Evolution of the Right Ventricular Potentials During Infancy. ECG Findings Based on Follow-up of Normal Newborns

The standards for amplitude of R was and R/S ratios in right-and S waves in left precordial leads in the ECG as well as their interelationships were studied longitudinally in 56 infants during the first 15 months of life. It was found that the increase in amplitude of R waves during the first 4 months was due to a general increase in voltage. The upper normal limits for R in V3r was 20 mm in the first four months and 18 mm thereafter. These limits were somewhat higher and around 23 mm in V1. The 3 percentile limits were 4 mm for V3r and 5 mm for V1. The decrease in S amplitude with increasing age was more significant in V6 as compared to V5. The R/S ratio in V3r and V1 increased during the first two months and decreased after the age of 4-6 months. A ratio of 6 is the upper normal limit in V1 and 0.9 the lower limit for V1 and V3r. The upper limits for the sum of the right potentials for RV1+SV5 is 35 mm and 28 mm for RV1+SV6. The lower limits are 10 and 8 mm, respectively. The amplitudes of R waves in V3r and V1 in the neonates and at one month did not show a significant correlation with the same variables obtained thereafter. Thus, the R wave amplitude in infancy cannot bepredicted from the peopate values. On the other heand, there was a significant correlation between values obtained after the age of 2 months and the interrelationship was higher in V1 as compared to V3r. The use of the upper limits presented herein will make easier the decision for pathologic overloading of right ventricle during infancy.