o_1977r8vv9vk1ts2ms0kd8pksa.pdf

410 Y. Chiba et al.
Fig. 27.16. Blood flow in an inferior vena cava (IVC) in a case of fetal supraventricular tachycardia
the blood flow pattern in an IVC is almost same as
the normal sinus rhythm (Fig. 27.16).
Determination of Fetal Therapy According
to the Type of Tachycardia
Some types of fetal tachycardia can be diagnosed by
the Doppler waveform at the IVC. However, some
conditions were difficult to diagnose, for example,
Wolff-Parkinson-White Syndrome. It is necessary to
establish the etiology of the tachycardia when we select
an antiarrhythmic drug. We require a precise diagnosis
to consider the type of intrauterine fetal therapy.
We previously published some reports regarding
the differential diagnosis of fetal tachycardia by magnetocardiography
and direct fetal electrocardiography
(Fig. 27.17) [25±29].
IVC and Umbilical Vein Blood Flow
Patterns in High-Risk Fetuses
The occurrence of umbilical venous pulsations in abnormal
and normal pregnancies has been described
by several authors. Nakai et al. [30], Indik et al. [31],
and Gudmundsson et al. [32] reported pulsatile flow
in the umbilical vein with changes in the IVC blood
flow pattern in hydropic fetuses. Arduini et al. [33]
found that fetuses with absent end-diastolic velocity
in the umbilical artery who present with umbilical venous
pulsations deteriorate rapidly. In their study, fetuses
with umbilical venous pulsations developed abnormal
fetal heart rate patterns within a shorter time
than did fetuses with normal umbilical venous flow.
As already mentioned, umbilical venous pulsations
can be observed in normal pregnancies during the
first trimester, and Nakai et al. [22] found such pulsations
during the third trimester in normal fetuses.
They concluded that umbilical venous pulsations in
normal fetuses are due to pulsations of the umbilical
artery. Their theory was supported by the fact that
umbilical venous pulsations in normal fetuses were
observed only transiently and only in the free loop of
the umbilical vein.
We conclude that an abnormal blood flow pattern
in the venous system represents hemodynamic deterioration
in severely compromised fetuses.
Fig. 27.17. Averaged fetal magnetocardiography of Wolff-
Parkinson-White syndrome of the fetus