J. Copel

Assessment of Blood Flow Velocity Waveforms of the Pulmonary Circulation by Multigate Spectral Doppler Scanning and Traditional Pulsed Doppler Ultrasonography

Objective. To assess (1) pulmonary artery and peripheral pulmonary blood flow by using a multigate spectral Doppler system and standard pulsed color Doppler ultrasonography and (2) the reproducibility of peripheral pulmonary artery blood flow velocity waveforms. Methods. Thirty‐three women were enrolled in the study. Fetal pulmonary artery flow velocity waveforms were investigated by multigate spectral Doppler scanning and traditional pulsed Doppler ultrasonography plus color flow mapping. To establish the relationship between these 2 methods, we calculated the correlation coefficient, coefficient of variation, and limits of agreement. Results. The 2 methods were not significantly correlated. The range of measurement agreement for these 2 methods suggests that there is a significant difference between the main and peripheral pulmonary artery blood flow, and the difference should be taken into account in the interpretation of Doppler flow velocity studies of the pulmonary artery. Conclusions. Multigate spectral Doppler scanning with power Doppler imaging may be a better way to assess the average flow impedance in a highly vascularized organ. This technique supplies a large number of Doppler signals in the region of interest and offers a quantified range of Doppler measurements, improving our understanding of fetal hemodynamics.

The effect of intravascular blood transfusion on the flow velocity waveform of the hepatic venous system of the anemic fetus

Our objective was to assess flow velocity waveforms of the portal venous system of the anemic fetus prior to and immediately following intravascular transfusion. Color-guided pulsed Doppler was used to obtain flow velocity waveforms from the fetal portal vein in 14 anemic fetuses that were transfused in utero for rhesus alloimmunization The portal vein velocity pattern was defined as continuous when no change in velocity during the cardiac cycle was noted. It was defined as pulsatile when a deflection of the wave was present. The flow velocity waveforms were quantified by using the ratio between the peak (highest, H) and the nadir (lowest, L) velocities (H/L ratio). Fourteen intravascular transfusions were performed. Gestational age ranged from 19.5 to 35 weeks (mean +/- SD, 26.7 +/- 5.3 weeks). The hematocrit ranged from 5.9 to 31.2% (mean +/- SD, 20.3 +/- 9%) prior to transfusion; after transfusion it was between 24.8 and 56.7% (mean +/- SD, 42 +/- 10.4%). In six cases (43%) the waveforms were pulsatile prior to transfusion; in the other eight (57%) they were continuous. The pulsatile pattern was present following transfusion in 13 cases (93%, p < 0.05). The mean of the H/L ratio was 1.3 +/- 0.38 prior to transfusion and 2.0 +/- 0.86 after transfusion (p < 0.05). Because the portal vein has continuous non-pulsatile flow in the normal fetus, the presence of pulsatility in the waves of six anemic fetuses (43%) may suggest portal hypertension. Compared to normal fetuses, there was an increased number of cases with pulsation, and even more so after transfusion. The pattern corresponds to findings in children with portal hypertension.