Neonatal circulatory changes: an echocardiographic study.

Serial echocardiograms were performed in the first three days of life on 38 normal full-term infants. Right ventricular systolic time intervals were measured from the pulmonic valve echogram and left ventricular systolic time intervals were determined from the aortic valve echogram. The heart rate, left ventricular pre-ejection period (LPEP), left ventricular ejection time (LVET), and LPEP/LVET ratio showed insignificant variation with increasing postnatal age. The right ventricular pre-ejection period (RPEP) shortened, the right ventricular ejection time (RVET) lengthened, and the RPEP/RVET ratio decreased with increasing age. The findings suggested that alterations in the RPEP/RVET ratio reflected the decreasing pulmonary artery diastolic pressure and pulmonary vascular resistance of the early neonatal period and may be valuable in the noninvasive evaluation of the newborn's pulmonary vascular bed.