Dilation of the ductus venosus by stent implantation increases placental blood perfusion in fetal sheep

Abstract

The reduction of resistance to flow in the ductus venous (DV) and a decrease of blood supply to the liver serve for the survival of the fetus during hypoxia. The present study investigated the influence of the increased diameter of the DV on placental blood perfusion. In 15 ewes with twin pregnancies at gestational ages of 117 +/- 4 days, a stent (4 or 5 mm) was placed into the DV of 1 twin (DV(stent) group) under ultrasound guidance. Blood flow rates in the umbilical vein (UV) and DV of both fetuses were measured using Doppler ultrasound. Eight pairs of twin fetuses were included for the final analysis. The dilatation of the DV increased the blood flow volume rate passed through the DV from 136.61 +/- 41.07 to 398.93 +/- 86.62 (mL/min(-1), P < .0001) and also significantly increased placental blood perfusion from 454.35 +/- 143.0 in control twin to 663.56 +/- 167.36 in the DV(stent) group (P < .05, mL/min(-1)), respectively. The DV/UV ratio increased from 30.6 +/- 11.6% in the control group to 58.9 +/- 11.6% in DV(stent) gemini (P < .0001). The positive effect of DV dilation on the placental blood perfusion was stable and could be observed up to 3 weeks after the operation. The dilatation of the DV by means of stent implantation in the DV increased the blood flow volume rate in the umbilical vein. Fetal surviving mechanism, the increase of DV shunting rate including redistribution of the blood flow in the liver with a reduction of DV resistance to flow, could have a second effect: the improvement of reduced placental blood perfusion during hypoxia.