To evaluate serial changes in superior vena caval (SVC) flow in early human neonates, we performed two-dimensional echocardiographic examination in 15 fullterm infants (36.6 ± 1.1 weeks' gestation, 3310 ± 570 gm' birth weight) at 2, 12, and 24 hours of age. SVC flow was obtained from the right supraclavicular fossa along with the electrocardiogram and respiration curve, and 3 to 5 cardiac cycles of expiratory phase were analysed. The antegrade blood flow during ventricular systole (S) and diastole (D) and retrograde one during atrial contraction (A) were confirmed, and their peak velocity and flow velocity-time integral (peak S and S area, peak D and D area, peak A and A area, respectively) were calculated. End-diastolic and end-systolic right ventricular volume (RVEDV and RVESV, respectively) were also calculated by bi-plane Simpson's rule using the apical four chamber and parasternal short axis views, and then right ventricular stroke volume (RVSV), subtracted RVESV from RVEDV, was obtained. The values of the peak S (mean± SD: 2h; 32.6 ± 6.2, 12h; 33.5 ± 5.4, 24h; 39.9 ± 8.1 cm/sec), S area (2h; 5.6 ± 1.1, 12h; 6.2 ± 0.7, 24h; 6.8± 1.2 cm), and D area (2h; 1.7 ± 0.8, 12h; 2.1 ± 0.6, 24h; 2.4 ± 0.7 cm) increased significantly at 24 h than those at 2 h of age. There were no significant changes of heart rate, peak D, peak A, and A area. Both the peak S and S area correlated positively with RVEDV and RVSV, but the others did not. We previously reported that the RVEDV significantly increased at 24 h, which mechanism was not clear at thAt time. Our present results suggest that, in early human neonates, volume load to the right ventricle increases at 24 h of age, and that antegrade blood flow during ventricular systole relates more closely to the preload to the right ventricle than that during ventricular diastole does.
