Venous pulsation in the fetal left portal branch: the effect of pulse and flow direction

Abstract

ABSTRACT

Fetal cardiac output, distribution to the placenta and impact of placental compromise

“…This is in keeping with other mechanisms seen in such fetuses: reduced size of and shunting through the foramen ovale 7,20 , increased resistance in the pulmonary circuit 21 , with correspondingly less venous return to the left heart, and retrograde blood flow at the aortic isthmus 7,22 to further supply the aortic arch and carotid arteries with right ventricular blood via the ductus arteriosus. A shift to the left of the watershed area between portal and umbilical venous supply to the liver 23,24 and an augmented blood velocity in the hepatic artery 25 will change the fetal circulation in the same direction. These are mechanisms of redistribution but also of increased recirculation of umbilical blood in the fetal body, which correspond to more extensive oxygen extraction.…”

“…• in 56 recordings and the median was 16 (IQR, [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] • in the remaining 141. The fetoplacental blood flow was calculated as π · (D/2) 2 · V wmean , and its fraction of the CCO was calculated as a percentage.…”

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).…”

“…Conversely, the high compliance of the sizeable intraabdominal umbilical vein in late pregnancy makes pulsation a rare event. The commonly recorded pulsation in the portal system during the second half of a normal pregnancy 18,23 may have a similar reason: the transverse portal sinus (left portal branch) has a considerably smaller dimension compared to the umbilical vein 24 . 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 .…”

“…An increased tone in the vessel wall due to adrenergic stimulation acts in the same direction. Thus compliance 13 , together with velocity direction 24 and differences in impedance at venous junctions 14,15 , are important issues when interpreting pulsations in a clinical setting.…”