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Dilatation of the ductus venosus in human fetuses: ultrasonographic evidence and mathematical modeling
Ist Teil von
American journal of physiology. Heart and circulatory physiology, 1998-11, Vol.275 (5), p.H1759-H1767
Ort / Verlag
United States
Erscheinungsjahr
1998
Quelle
MEDLINE
Beschreibungen/Notizen
1 Department of Obstetrics and
Gynecology, San Paolo Biomedical Sciences Institute, University of
Milan, 20142 Milan; and
2 Department of Bioengineering
and Centro di Bioingegneria e Innovazioni Technologiche in
Cardiochirurgia, Politecnico di Milano and Hospital San Raffaele,
20132 Milan, Italy
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.
fetal circulation; model simulation; ultrasound; sphincter