Increased pulsatility in the fetal ductus venosus is not related to altered cardiac strain in high-risk pregnancies

Objective: Blood flow velocity patterns in fetal veins are considered to reflect cardiac function, but have not been convincingly documented. The aim of this study was to generate reference values for fetal cardiac strain and compare it with results in fetuses with signs of increased venous pulsatility.Methods: Cardiac four-chamber loops were prospectively stored and analyzed for strain and strain rate in a cohort of 250 healthy fetuses. The results were compared with recordings in 38 fetuses with increased vascular impedance in the umbilical artery, including several with abnormal blood flow velocities in the ductus venosus (DVs) and umbilical vein.Results: In the control group, strain rate was slightly higher in the right ventricle, but strain and velocities were similar. There was a significant effect of frame rate on the values of strain and strain rate, but not on velocity. No differences in cardiac strain or strain rate were observed between the control group and the compromised fetuses. There was no correlation between changes in venous blood flow and cardiac strain.Conclusions: Increased venous pulsatility was not related to fetal cardiac strain. This might indicate that the DVs does not primarily open due to increased central venous pressure and that cardiac strain is affected late in the process of moderate fetal hypoxia.