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a Chapter 33 Doppler Echocardiography for Managing Congenital Cardiac Disease 491
Color flow and spectral Doppler modes can substantially
assist 2D echocardiography in defining various
congenital cardiac malformations. This section presents
the Doppler characterization of anomalous hemodynamic
patterns for commonly encountered congenital
heart diseases in the fetus. The categorization
used here is imperfect and somewhat arbitrary, as
many of these conditions are characterized by multiple
lesions. Furthermore, this review is brief, as a
comprehensive discussion of these conditions is beyond
the scope of this chapter.
Fig. 33.5. Doppler-derived right ventricular dP/dt in fetuses
with ductal constriction compared to fetuses with nonimmune
hydrops (NIHF). Filled circles survivors, crosses nonsurvivors.
(Reprinted from [32] with permission)
diographic assessment of the fetal cardiac function as
a tool of prognostication.
Demonstration of abnormal direction of blood
flow in the central vascular channels may assist in defining
complex cardiac lesions. For example, the presence
of reverse flow in the ductus arteriosus in cases
where the pulmonary outflow is difficult to image is
diagnostic of pulmonary atresia. Chiba and associates
[14] reported the utility of color flow mapping, including
the depiction of abnormal flow directionality
for identifying intricate malformations.
4. High velocity and turbulent flow. Abnormal
magnitude of flow velocity is pathognomonic of cardiac
pathology. As a general principle, flow velocity
is increased in the alternative flow paths as they accommodate
the flow diverted from hypoplastic chambers
and atretic flow channels. Thus with tricuspid
atresia flow velocity is increased in the mitral orifice
and the aorta. In contrast, flow velocities across the
atretic channels and in the hypoplastic chambers are
absent or decreased (during the initial phase of the
lesion). With fetal congenital heart block, the aortic
and pulmonic flow velocity and flow are significantly
increased. Stenotic lesions present a different problem.
If there are no alternative circulatory paths, inflow
in a vascular system equals outflow.
Cardiac Position
Anomalies of the cardiac position are rare. Fetal cardiac
malposition may be intrathoracic or extrathoracic.
Intrathoracic malposition may result from (1)
secondary displacement of the heart due to a thoracic
mass or fluid collection, which may lead to pseudodextrocardia;
or (2) visceral malrotation resulting in
dextrocardia. Extrathoracic malposition results from
defective development of the anterior thoracic wall or
the diaphragm causing ectopia cordis. Although these
conditions are recognized by 2D echocardiography,
color and spectral Doppler modes assist in defining
altered vascular connections and associated cardiac
malformations.
Intrathoracic Cardiac Displacement
The most common malposition of the heart is probably
related to a mediastinal shift caused by a spaceoccupying
intrathoracic lesion such as a left diaphragmatic
hernia (Fig. 33.6). With this condition,
although the heart is displaced to the right hemithorax,
the cardiac apex remains oriented to the left. The
diagnosis is established by sonographic demonstra-
Doppler Echocardiographic
Assessment of Specific Cardiac
Anomalies
Fig. 33.6. Color Doppler depiction of pseudo dextrocardia
secondary to left diaphragmatic hernia. SP fetal spine, L
left, R right. The fetal heart is located on the right side of
the thorax; its normal position on the left is occupied by
the stomach. Note that despite the left displacement the
cardiac apex remains directed to the left