Diagnostic ultrasound ( PDFDrive )

1290 PART IV Obstetric and Fetal Sonography
RV
LA
FIG. 37.35 Congenitally Corrected Transposition of Great Arteries.
An apical four-chamber view shows the morphologic right ventricle
(RV) and morphologic left ventricle (LV) located on the incorrect sides
of the heart. This is evidenced by identifying the atrioventricular valve
lealets inserting (arrow) on the left side of the heart in a more apical
location than the right-sided atrioventricular valve lealet insertion.
LA, Left atrium; RA, right atrium.
Sonographic diagnosis depends on demonstrating that the
great vessels exit the heart in parallel, rather than crossing in
the normal fashion. his is optimally seen in a long-axis or
short-axis view of the great vessels. A three-vessel view is also
useful because only one great vessel (aorta) is usually visualized
at this level, in this setting.
Most neonates with D-TGA require immediate treatment.
Initially, a temporizing shunt may be created before deinitive
treatment, frequently with the arterial switch procedure. With
surgical intervention, 12-month survival can be expected in
80%. 149 Early intervention (within 3 days of life) when using the
arterial switch operation is optimal and is associated with an
operative mortality below 2%. Major morbidity and cost increase
daily thereater. 150
Corrected transposition (L-TGA) is characterized by A-V
discordance with V-A discordance (Fig. 37.35). It comprises 1%
of CHD and 20% of cases of fetal TGA. 47 he aorta, which arises
from the let-sided, morphologic right ventricle, is anterior and
to the let of the pulmonary artery. he pulmonary artery arises
from the right-sided, morphologic let ventricle. VSD and
pulmonic stenosis occur in approximately half the cases. 124,151
Malformation and inferior displacement of the morphologic
tricuspid valve may be present. Pathophysiologically, the low
of blood through the heart to the pulmonic and systemic circulations
is normal, even though the morphologic right ventricle is
on the let and the morphologic let ventricle is on the right.
he antenatal sonographic diagnosis rests on demonstrating
a parallel arrangement to the great vessels, similar to D-TGA.
Diferentiating D-TGA from L-TGA entails identiication of the
morphologic right and let ventricles. he moderator band will
be seen on the anatomic let side. In addition, the tricuspid valve
will be situated on the anatomic let side, so its more apical septal
LV
RA
lealet should be identiied. Associated cardiac defects are common
and diverse, including VSD, pulmonary stenosis or atresia, ASD,
DORV, tricuspid valve anomalies, dextrocardia, mesocardia, and
situs inversus. Fetal A-V block is common with TGA. 152
In the absence of associated cardiac anomalies, patients
with corrected TGA may remain asymptomatic throughout their
lives.
Anomalous Pulmonary Venous Return
APVR can be divided into two subgroups: total anomalous
pulmonary venous return (TAPVR), in which none of the
pulmonary veins drains into the let atrium, and partial anomalous
pulmonary venous return (PAPVR), in which at least one
of the pulmonary veins has an anomalous connection. TAPVR
constitutes 2.3% of cases of CHD. 153,154 he four types of anomalous
pathways are as follows:
1. he pulmonary veins drain into a vertical vein that empties
into the innominate vein and then into the SVC.
2. he pulmonary veins drain into the coronary sinus and then
into the right atrium.
3. he pulmonary veins drain directly into the right atrium.
4. he pulmonary vein drains into the portal vein and into the
IVC via the ductus venosus.
Embryologically, TAPVR is thought to result from failure of
obliteration of the normal connections between the primitive
pulmonary vein and the splanchnic, umbilical, vitelline, and
cardinal veins. TAPVR is associated with AVSDs and polysplenia
and asplenia syndromes.
he antenatal sonographic diagnosis of TAPVR is diicult
because the anomalous veins are generally extremely small and
variable in their course. Oten the irst sign of APVR is mild
right ventricular and pulmonary artery prominence, in which
case a careful search for the four normal pulmonary veins should
be undertaken. 155 his can be diicult because the two inferior
pulmonary veins are usually more diicult to visualize than the
two superior veins, even in a normal fetal heart. Color and spectral
Doppler ultrasound are helpful in documenting the normal
pulmonary venous anatomy and in detecting and following the
anomalous connections (Fig. 37.36).
he diagnosis of TAPVR is suspected when no pulmonary
veins are seen entering the let atrium (Fig. 37.37). A small let
atrium resulting from decreased blood return and lack of normal
incorporation of the common pulmonary vein into the let atrium
is also suggestive of TAPVR. Approximately one-third of patients
with TAPVR have associated cardiac anomalies. 156 Right atrial
isomerism is common. Associated extracardiac anomalies include
gut malrotation and midline liver and stomach. 157,158 TAPVR
causes minimal hemodynamic disturbance in utero, although
hydrops occasionally results. Let untreated, the majority of infants
die before 1 year of age. 133 Although PAPVR has also been
diagnosed in utero, the diagnosis is more diicult and can be
made only when pulmonary veins are seen entering the let atrium
as well as the right atrium or an accessory pathway to the right
atrium. 159 APVR is associated with high morbidity and mortality,
largely because of the high incidence of additional cardiac
anomalies. 157,159 Surgical correction of TAPVR is associated with
an operative mortality of nearly 20%. 160