Postnatal Changes in Left Ventricular Performance in Early Neonatal Life

Purpose : This study was undertaken to investigate changes in cardiac performance in early neonatal life by observing the changes of left ventricular(LV) function and volume according to the size of ductus arteriosus. Methods : The study group consisted of 21 full-term Cesarean section neonates who were admitted to the nursery of Korea University Hospital. We serially investigated the patency and size of the ductus at 2, 24, 120 hours after birth by two-dimensional echocardiography. The standard two-dimensional tracings of LV volume were obtained under the guidance of apical twoand four-chamber views. LV end-diastolic and end-systolic volumes were calculated using a biplanar Simpson's method. Results : LV end-diastolic volume was highest(3.44±0.4mm) at 2 hours of age(P<0.01), being constant from 24 to 120 hours. LV contractility, indicated by the mean normalized systolic ejection rate, remained constant during the whole period of investigation. The size of the ductus arteriosus was maximal at 2 hours after birth, and decreased significantly at 24 hours of age (P<0.01). The size of ductus arteriosus demonstrated a close linear correlation with the left ventricular end-diastolic volume(y=0.17x+2.92, r=0.59 : P<0.01). Conclusion : Changes in LV end-diastolic volume soon after birth depend on changes in ductus arteriosus flow, which in turn is affected by ductal diameter. Upon patency of the ductus arteriosus, the newborn left ventricle operates at maximal performance with only a limited capacity to increase contractility. (J Korean Pediatr Soc 2000;43:1168-1173)