Serial Changes of Doppler Echocardiographic Transvalvular Velocity during the Neonatal Period in Full Term Neonates

Kim, Woo Taek; Hyun, Myung Chul; Lee, Sang Bum

Abstract

PURPOSE
We performed this study to compare serial measurements which relate to both ventricular functions in full term neonates for the first three weeks after birth.
METHODS
Echocardiographic and pulsed Doppler studies were performed for 20 newborns during the first 36 hours of life, and subsequent serial studies in the second (n=13) and third(n=12) weeks of life. Evaluation included measurements of both isovolumic relaxation times(IVRT), peak E and A velocities, E and A areas, velocity-time integrals(VTI) across both atrioventricular valves, and peak velocities, peak accelerations, times to peak velocity(acceleration time, AT) and velocity-time integrals across both semilunar valves. Both isovolumic relaxation times were evaluated by using dual M-mode determination of the interval between closure of the semilunar valves and opening of the arterioventricular valves.
RESULTS
Heart rates for three groups were similar and pulmonary artery velocities consistent with patent ductus arteriosus were present in 15 of 20 cases(75%) during the first 36 hours of life but in none thereafter. Significant differences existed for RIVRT/ RR, which shortened from 92.9 msec in the initial study to 53.2 msec (p<0.001), at week two. Tricuspid A/E peak velocity ratio decreased from 1.30 to 1.08(p<0.001), A/E area ratio decreased 1.78 to 1.06(p<0.001), VTI/ RR increased from 12.56 cm to 14.64 cm (p<0.01), pulmonary VTI/ RR increased from 17.62 cm to 23.31 cm(p<0.01), and pulmonary AT/ RR prolonged from 75.0 msec to 121.3 msec(p<0.001). These changes suggest that postnatal rapid increase in right ventricular compliance and rapid fall in pulmonary vascular resistance and pressure occurred during this period. Changes in RIVRT/ RR correlated inversely with tricuspid VTI/ RR, pulmonary AT/ RR and VTI/ RR with their p values approaching significance(p=0.05-0.1), suggesting somewhat of an influence of afterload reduction in addition to compliance change on diastolic events. Also significant differences existed for LIVRT/ RR, which shortened from 63.5 msec at week two to 56.6 msec(p<0.05) at week three, mitral VTI/ RR, which increased from 14.10 cm to 16.45 cm(p<0.01) and aortic peak acceleration/ RR, which increased from 23.81 m/s2 to 30.90 m/s2(p<0.01). But no significant changes were noted in mitral A/E peak velocity ratio and area ratio, aortc peak velocity, AT/ RR and VTI/ RR, and pulmonary peak velocity and peak acceleration/ RR. In tricuspid valve measurements, the A/E peak velocity ratio and area ratio were shown to be consistently above unity, whereas those of mitral valves were below unity which reflect that of right ventricular compliance must have been still lower than that of the left ventricle during this period.
CONCLUSIONS
This serial study in newborns demonstrates that the expected postnatal physiologic changes in ventricular compliance and pulmonary vascular resistance and pressure can be evaluated by Doppler echocardiography.