o_1977r8vv9vk1ts2ms0kd8pksa.pdf

488 D. Maulik
report in utero worsening of cardiac anomalies; they
observed discrete coarctation with a normal aortic arch
noted first at 21 weeks deteriorating to a markedly hypoplastic
aortic arch by 34 weeks. Subsequently, a multiplicity
of reports appeared. These include (a) development
or progression of pulmonary stenosis in the fetus
with advancing gestation [18±21]; (b) development of
dilated cardiomyopathy later in pregnancy when no abnormalities
were observed at 20 weeks [22]; (c) development
of left heart hypoplasia syndrome despite normal
echocardiographic scan in early pregnancy [23±
25]; (d) intrauterine closure of foramen ovale [26];
and (e) development of right ventricular hypoplasia
[27]. In contrast to deterioration, there are infrequent
reports of improvement of cardiac lesions in utero;
these include: (a) improvement of left heart hypoplasia
because of progressive growth of the left heart during
gestation [21]; and (b) in utero closure of ventricular
septal defect [28]. There are important practical implications
of these observations. It is apparent that cardiac
assessment performed at midpregnancy may not ensure
the absence of cardiac malformation later in pregnancy
or at birth. In a pregnancy at a higher risk of cardiac
malformation, it may be prudent to repeat the examination
at mid third trimester. However, the cost-effectiveness
of a policy of cardiac scanning twice during
pregnancy in all cases referred for fetal echocardiographic
assessment remains undetermined.
Table 33.7. Anatomic correlates of Doppler hemodynamic
information
Hemodynamic information
Presence of normal flow
in expected location
Presence of flow in an
unexpected location
Absence of flow in an
expected location
Abnormally high-velocity
flow
Abnormal flow direction
Anatomic correlates
Corroborative of normal anatomic
image
Anatomic lesions: septal defects,
aneurysms
Nonfunctioning chamber;
hypoplasia; severe vascular
stenosis
Stenotic lesion, functional
constriction
Regurgitant flow ± valvular
incompetence; redirected
flow in vascular lesion
Doppler Characterization
of Congenital Cardiac Malformations
Doppler echocardiographic examination constitutes a
component of the overall assessment of the fetal
heart. This integrated approach is described in
Chap. 32. Doppler ultrasonography provides a range
of hemodynamic information (see Chap. 4) that
should be interpreted in terms of normal and abnormal
cardiac function and anatomy. An understanding
of the morphologic correlates of abnormal cardiac
Doppler flow patterns is helpful for diagnosing congenital
heart disease. These correlates are discussed
below and summarized in Table 33.7.
1. Absence of flow in expected locations. As discussed
in Chap. 4, some of the primary hemodynamic
information offered by Doppler insonation regards
the presence or absence of flow. The reliability of this
function depends on the instrumental characteristics
and setting and on the circumstances of the examination.
For example, the transducer frequency, gain setting,
and angle of insonation affect the ability of the
operator to identify and reliably conclude that there
is or is not flow. Thus one may spuriously fail to note
flow even when it exists because of an unfavorable
angle or low gain. Similarly, low-flow states may not
Fig. 33.1. Doppler color flow mapping of left ventricular
dilation preceding hypoplastic change. LV left ventricle, RV
right ventricle. Color Doppler shows flow in RVextending
to the ventricular apex. In contrast, flow could not be demonstrated
in most of the LVchamber, which shows marked
dilation and poor contractility. This condition developed
into left ventricular hypoplasia
be identified unless the device is optimized for such
function. Assuming that these factors have been taken
into consideration, color and spectral Doppler demonstration
of the absence of flow in an expected location
is helpful for diagnosing an existing or evolving
cardiac problem. The most remarkable example is the
absence of flow in one of the ventricles, which in
conjunction with the observation (by 2D imaging) of
the absence of an echo-lucent space in the ventricle is
diagnostic of left or right ventricular hypoplasia (see
below). We have also seen examples of progressive
ventricular developmental failure starting as a dilated
ventricular chamber with no discernible flow culminating
in left ventricular hypoplasia (Fig. 33.1). There
are other instances where Doppler depiction of the
absence of flow is suggestive of structural anomalies