THE EFFECT OF POSTNATAL TRANSITIONAL CIRCULATION ON ECHOCARDIOGRAPHY-DERIVED INDICES OF HEART FUNCTION IN HEALTHY NEONATES

Abstract

Novel echocardiography-derived indices (EDIs) of cardiac function are beginning to be utilized for studying the myocardial function in newborn infants. Several of these indices have been shown to be dependent on loading conditions. Immediate postnatal period in normal neonates is characterized by dramatic physiological hemodynamic changes, most notably reduction in right ventricular (RV) afterload and increase in left ventricular (LV) afterload. Before these EDIs are used in neonates suffering from pathological alternations in postnatal transition, it is important to understand whether physiologically normal changes associated with postnatal transition have any major influence on them. In this study, we sequentially measured conventional and novel indices of left and right ventricular systolic and diastolic function in a cohort of healthy neonates starting shortly after birth till end of 1st day of life, thus covering the period of peak changes transitional circulation. Antenatal consent was obtained from 15 pregnant women who presented to our maternity ward in labor at term gestation after having had an uncomplicated low risk singleton pregnancy. All infants but 1 infant was delivered vaginally. 3 infants had to be excluded - 1 was diagnosed with delay in transition shortly after birth, 1 was unexpectedly found to be large for gestational age and the mother of another infant developed acute postpartum hemorrhage. Remaining 12 well term neonates (mean wt. 3.49±0.53Kg) underwent 4 sequential echocardiograms at <0.5, 2.5, 8 and 22 hours of life. Images were collected using 2-D, color Doppler and tissue Doppler imaging and various EDIs of systolic [RV-S', TAPSE, LV-S’, LV ejection fraction (LVEF), LV speckle-tracking derived global longitudinal strain (LVGLS)], diastolic [E:A, E':A', E:E' (for each ventricle)], and global ventricular performance [MPI'] were measured. Pulmonary artery acceleration time (PAAT) was measured as a surrogate of pulmonary vascular resistance. Changes over time were analyzed using 1-way repeat measures ANOVA. In spite of significant changes in HR and PAAT over the study period, all systolic EDIs for both ventricles remained unchanged over time. Both S' velocities showed weak but significant linear correlation with HR. Among EDIs for diastolic function, E:E' was the only marker which remained unchanged for both ventricles throughout the study period (TABLE). We identified that in healthy newborns, RV-TAPSE, LVEF, LVGLS and E:E' were least affected by physiological alterations in HR and transitional circulation, and hence may be more suitable for use in disorders of postnatal transition.