Doppler echocardiographic observations of pulmonary and transvalvular velocity changes after birth and during the early neonatal period

To evaluate the qualitative and quantitative changes in Doppler velocities in the normal fetus and newborn, 61 echo Doppler studies were performed in 18 neonates, nine of whom were also studied as fetuses. Four studies were inadequate in fetuses (one pulmonary artery, two mitral, and one tricuspid) and some post natal studies were inadequate due to inability to separate atrioventricular valve E and A velocity component waveforms (one tricuspid, three mitral). Heart rates for fetuses and newborns more than 24 hours of age and less than 24 hours of age were similar. Pulmonary artery diastolic velocities consistent with patent ductus arteriosus were present in 11 of 12 examinations at less than 6 hours of age, in 5 of 13 examined at 6 to 24 hours of age, and in 2 of 27 examined after 24 hours of age. Pulmonary artery times to peak velocity were similar in fetuses, m = 46, SD = 3 msec, and in neonates less than 6 hours of age, m = 51, SD = 13 msec, but lengthened significantly, p < 0.05, at 6 to 24 hours (m = 69, SD = 14 msec). These changes are probably due to the dramatic changes in pulmonary vascular pressure that occur after birth. Data from 6 to 24 hours and >24 hours (m = 78, SD = 13 msec) were similar. Significant differences existed for transmitral valve E A ratios, which increased from m = 0.85 in utero to m = 1.17 (p < 0.05) after birth, with no significant change thereafter. This change was due to significant increases in transmitral valve E and A velocity, E > A. These data probably reflect post natal increases in transmitral flow and decreases in left ventricular compliance. No significant changes were noted in tricuspid velocity data, peak aortic velocities, or peak pulmonary velocities. This serial study in fetuses and newborns demonstrates that the expected post natal physiologic changes in pulmonary vascular resistance and ventricular compliance can be evaluated by Doppler echocardiography. Normal data are shown that compare well with those obtained in other studies of fetuses² and newborns.¹⁴ Normal and serial pulmonary artery time to peak velocity data for fetuses and newborns are now provided by this study.