Our objectives were to describe the normal pulmonary venous blood flow velocity waveform and to establish reference ranges for the second half of pregnancy in healthy human fetuses. A total of 123 women with uncomplicated pregnancies of between 20 and 40 weeks were examined, using a combined color-coded Doppler and two-dimensional real-time ultrasound system. Pulsed Doppler flow velocity waveforms of pulmonary venous drainage into the left atrium were obtained from a transverse cross section of the fetal chest at the level of the cardiac four-chamber view. All waveforms were obtained during fetal apnea. The success rate in obtaining the pulmonary venous waveform was 81%. The waveform displayed a biphasic forward flow profile with a systolic and diastolic component. Peak systolic, peak diastolic and time-averaged velocities demonstrated a gestational age-related rise, whereas the peak systolic/peak diastolic ratio showed a gestational age-related reduction. The nature of the fetal pulmonary venous flow velocity waveform pattern suggests positive pressure towards the left atrium throughout the cardiac cycle. We speculate that an increase in volume flow and the pulmonary venous pressure gradient play a role in the gestational age-related changes in pulmonary venous flow velocities.
In a twin pregnancy discordant for trisomy 18, the affected fetus at 13 weeks' gestation had an increased nuchal translucency thickness and reversed end-diastolic ductus venosus flow. At 20 weeks' gestation there was no nuchal edema and Doppler study of the central venous vessels demonstrated normal waveforms. The findings support the hypothesis that one of the mechanisms in the development of increased nuchal translucency is temporary cardiac strain.
ABSTRACT. Ultrasonic visualization of the human fetal subdiaphragmatic area demonstrated anatomical relationships, different from descriptions in the literature. Four human fetal postmortem specimens at 18, 26, 28, and 34 wk of gestation were examined to ascertain morphologic details of intra-and perihepatic vasculature. Drawings of these dissected preparations were compared with ultrasonic images from the same region. With both methods the presence of a venous vestibulum immediately proximate to the diaphragm could be demonstrated. The abdominal inferior vena cava ends in a funnel-like structure, which also contains the orifices of the hepatic veins, the ductus venosus, and a phrenic vein. A considerable variability in Doppler flow recordings could result from blood propelling out of these various vessels into the vestibulum. It is, therefore, suggested that information on blood-flow velocities in venous hepatic vessels should be obtained more distally in the separate vessels and not at the entrance into the right atrium. ( Recently, a sonographic method to obtain Doppler velocity wave forms from the human fetal IVC by ultrasonic guidance was described (1). The proposed site to direct the Doppler beam is situated just proximate to the RA. However, visualization of this area by two-dimensional real-time ultrasound demonstrated anatomical relationships that did not correlate with morphologic descriptions in the literature (2-7). The IVC is considered to course straight through the diaphragm into the RA, although other veins, such as the DV and the hepatic veins, discharge separately into this straight vessel at different locations along its subdiaphragmatic course through and above the fetal liver (4- During Doppler studies of the IVC immediately proximate to the RA, other flow velocity wave forms often were encountered, in particular from the left hepatic vein and DV. Also an unexplained large SD was found while analyzing IVC wave form parameters from this site (8). Two studies suggest a clinical importance of these parameters in cases of arrhythmias and growth retardation (1,9).The aim of the present study was to ascertain the exact anatomical relationship between IVC, DV, and the hepatic veins in the human fetus in the diaphragmatic and subdiaphragmatic area. MATERIALS AND METHODSPostmortem specimens of four human fetuses at 18, 26, 28 and 34 wk of gestation, taken at random, were examined.The abdominal cavity had been opened in all fetuses during autopsy, and in three fetuses heart and lungs had been removed immediately superior to the diaphragm to exclude cardiac anomalies. No macroscopically detectable congenital abnormalities were found.The umbilical vein served as a guide for the exposure of the hepatic vasculature. After the removal of surrounding liver parenchyma, the blood vessels in the hepatic region around and above the intra-abdominal part of the umbilical vein were carefully dissected, so they could be traced to their origin. Drawings were made of two of four specimens (Figs. 1-3). Interest was pa...
Reproducibility and inter-observer variability of intra- and extra-abdominal umbilical venous flow velocity and left portal venous flow velocity as well as heart-synchronous waveform pulsations in these vessels were studied in 23 women at 34-38 weeks of normal pregnancy.Limited reproducibility, expressed by large intra-patient coefficients and limits of agreement between two observers, was established for all standardized recording sites. Pulsations, defined as negative venous deflections of at least 10% of the mean velocity, were demonstrated at all locations ranging from 19.6% of the measurements at the free-floating loop of the umbilical vein to 78.4% of the measurements at the left portal vein. The present study shows that the limited reproducibility of venous flow velocity waveforms should be taken into consideration, and that the presence of pulsations can be demonstrated in normal late pregnancy.
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