Dilatation of the ductus venosus in human fetuses: ultrasonographic evidence and mathematical modeling

Abstract

Autonomic regulation of blood flow through the fetal ductus venosus has been suggested, but the existence of a sphincter at the ductal entrance in human fetuses has yet to be established. In this paper two cases of apparent ductus venosus dilatation in two growth-restricted human fetuses are reported. Prolonged ultrasonographic analysis (45 min) showed rapid and substantial changes (>80%) of ductal diameters. Pulsed Doppler analysis was used to investigate flow velocity in the ductus venosus and umbilical vein for both normal and dilated conditions. Dilated conditions caused manifest modifications of velocity tracings. Systolic peak velocity in the ductus did not change visibly, whereas velocity at the atrial contraction showed evident reduction; consequently, pulsatility indexes increased. Furthermore, the umbilical vein presented flow velocity pulsations. The mean blood flow rate through the ductus seemed to increase substantially (>70%) for high dilatation. To investigate these findings further, we performed simulations of ductal dilatation by means of a lumped-parameter mathematical model of the human fetal circulation. Model results agreed with clinical evidence and confirmed the relationship between ductal dilatation and the observed velocity alterations. Simulated systolic peak velocity slightly increased for small dilatation (<30%), whereas atrial velocity was reduced when the ductus dilated. Furthermore, the model indicated that umbilical venous pressure decreases for increasing dilatation, whereas no change occurs in the central venous pressure. The present results seem to indicate the presence of active dilatation of the ductus venosus in human fetuses.

Endothelin‐induced constriction of the ductus venosus in fetal sheep: developmental aspects and possible interaction with vasodilatory prostaglandin

“…While confirming the importance of extrinsic factors -resistance of the hepatic vascular district, magnitude of the umbilicocaval pressure gradient, blood viscosity -for the control of ductal flow (see Kiserud, 1999), this new line of investigation has yielded direct evidence, both in animals and humans, of an active tone regulation in the putative sphincter region as well as in the remainder of the vessel (Bellotti et al, 1998;Kiserud et al, 2000a). Coincidentally, it has demonstrated that ductus closure is delayed in preterm compared to term infants and, moreover, has ascertained that this sign of prematurity may subside after antenatal treatment with corticosteroids (Fugelseth et al, 1998;Loberant et al, 1999;Kondo et al, 2001).…”

“…Recent advances in ultrasound imaging have shed light on this problem (Bellotti et al, 1998;2000;Kiserud, 1999;Kiserud et al, 2000b). While confirming the importance of extrinsic factors -resistance of the hepatic vascular district, magnitude of the umbilicocaval pressure gradient, blood viscosity -for the control of ductal flow (see Kiserud, 1999), this new line of investigation has yielded direct evidence, both in animals and humans, of an active tone regulation in the putative sphincter region as well as in the remainder of the vessel (Bellotti et al, 1998;Kiserud et al, 2000a).…”

The effect of vascular constriction on umbilical venous pulsation

“…We found visible pulsation in the umbilical vein at the abdominal inlet (umbilical ring) in 242/279 participants (87%, 95% CI 82-90), which was more common than in the cord (43/198, 22%, 95% CI [16][17][18][19][20][21][22][23][24][25][26][27] and in the intra-abdominal section of the vein (84/277, 30%, 95% CI 25-36) (P < 0.001) (Figure 2).…”

“…During abnormal cardiac physiology 25,26 an augmented atrial contraction is transmitted along the inferior vena cava and ductus venosus, which act as a transmission line to reach the intra-abdominal umbilical vein 9,15 . During hypoxia the ductus venosus distends 27,28 and reduces the reflections that normally take away most of the pulse energy before it reaches the umbilical vein 15 . A congestion in the umbilical vein (commonly seen in such situations 29 ) stretches the wall, or a twisting of the cord 30 causes a reduced compliance, which enhances the induction of velocity pulsation.…”

Ductus venosus Doppler study in fetuses with homozygous α‐thalassemia‐1 at 12 to 13 weeks of gestation

“…The vessel forms a preferential streaming of oxygenated blood to the foramen ovale and to the left heart and brain 6 . The ductus venosus appears to have a sphincter-like action that can regulate the amount of oxygenated blood shunted to the foramen ovale 10 .…”