BLOOD-FLOW VELOCITY WAVE-FORMS IN THE MATERNAL HEPATIC VEIN DURING PREGNANCY

Objective: The purpose of this study was to establish the relationship between the various blood flow velocity components in the maternal he patic veins (HV) and gestational age during normal pregnancy. Methods: A total of 52 persons (9 men, 10 nonpregnant and 33 pregnant women) u nderwent Doppler examination of hepatic veins. Three resistance indice s were calculated from the blood flow velocity waveforms: RIo (Vs - Vo )/Vs; RId = (Vs - Vd)/Vs; RIa = (Vs - Va)/Vs [Vs: systolic maximum vel ocity; Vo: maximum velocity at tricuspid valve opening (right atrial o verfilling); Vd: maximum velocity in early diastole (opening of the tr icuspid valve and flow of blood from the right atrium to the right ven tricle); Va: maximum reverse blood flow velocity at atrial systole]. R esults: The HV flow velocity waveform depicts a pulsatile pattern, whi ch in the male and in the nonpregnant female consists of two forward a nd one reverse component. In pregnancy, this pattern gradually changes to a flat waveform without phasic oscillations. The RIo and RId showe d moderate to good correlation with gestational age (correlation coeff icients R = -0.66 and R = -0.78 in the supine position; R = -0.53 and R = -0.39 in the left lateral position). However, both indices were ra ther variable in each of the groups examined. The most significant cha nges during pregnancy were found in RIa which had the highest correlat ion with gestational age (correlation coefficient R = -0.81 in the sup ine position; R = -0.71 in the left lateral position). Conclusions: Th e hepatic vein blood flow velocity waveforms change significantly duri ng normal pregnancy. Several mechanisms were discussed which might be involved to produce these changes.