Serial echocardiography during the first 3 mth of life in normal neonates

Echocardiography was performed in 13 normal neonates on the first day of life and repeated after 1 wk, 1 mth and 3 mth. Measurements were made of cardiac chamber size and wall thickness, mitral, tricuspid and pulmonary valve motion, right and left ventricular systolic time intervals, and of fractional left ventricular shortening (%deltaS) and mean velocity of circumferential fibre shortening (mean Vcf). During the study there was a relative decrease in right ventricular cavity size and wall thickness with an increase in the pulmonary valve EF slope, indicating a fall in pulmonary artery pressure with regression of the right ventricle. Left ventricular size and thickness increased while LVET became longer, possibly the consequence of an increasing left ventricular afterload. There was not a significant change in %deltaS and mean Vcf during the study period. The greatest change from right to left ventricular preponderance occurred between 1 wk and 1 mth of life and was accompanied by changes in the mean frontal QRS axis of the electrocardiogram. The study shows that significant changes occur in the echocardiogram during the first 3 mth of life; neonatal echocardiograms should be interpreted not only in relation to the baby's weight, but also to its age.