Noninvasive Assessment of the Early Transitional Circulation in Healthy Term Infants

Abstract

Background: The early neonatal circulatory transition usually occurs smoothly but occasionally it is incomplete or reverts to the fetal state of high pulmonary vascular resistance, resulting in significant neonatal morbidity. Objective: To define the normal values for echocardiographic parameters during the early transitional circulation in term infants. Methods: Two-dimensional, M-mode, pulsed and color flow Doppler echocardiography was used to assess healthy term infants in the first 4 h of life. Left and right ventricular outputs (LVO and RVO) and myocardial performance indices (MPI), left ventricular fractional shortening, end-systolic diameter and end-diastolic diameter, ductal size, shunt and peak velocities, tricuspid regurgitation and left pulmonary artery diastolic velocities were documented. Results: A total of 21 normal term infants were assessed with median gestation of 39 weeks, birth weight of 3,470 g and postnatal age of 3 h and 22 min. The median echocardiographic values were LVO 193 ml/kg/min, RVO 216 ml/kg/min, left MPI 0.41, right MPI 0.63, and fractional shortening 29%. The ductus was patent in all 21 infants with a median size of 2.3 mm; ductal flow was bidirectional in 86% with median peak left-to-right velocity of 1.07 m/s. The median left pulmonary artery diastolic velocity was 0.31 m/s and physiological tricuspid regurgitation was present in all infants. Conclusion: This study defines normal values for echocardiographic measurements in healthy term infants during the first 4 h after birth. These normative data may be useful in early identification of infants with abnormal circulatory transition, allowing more rapid determination of cardiovascular dysfunction.