o_1977r8vv9vk1ts2ms0kd8pksa.pdf

a Chapter 33 Doppler Echocardiography for Managing Congenital Cardiac Disease 497
stenosis. The left atrium is small, with the foramen
ovale usually patent. The right ventricle and atrium
are enlarged because of hypertrophy and dilation.
The condition may evolve with advancing gestation,
so early echocardiographic examination may not detect
the problem. Although 2D and M-mode echocardiographic
examination can establish the diagnosis,
addition of color and spectral Doppler interrogation
is invaluable for defining the malformation
(Fig. 33.15). The cause of left heart hypoplasia is obscure,
but it is noteworthy that a similar malformation
can be created in animals by decreasing the interatrial
blood flow. Such an aberrant hemodynamic
phenomenon may be responsible in the human fetus
because of the secondary effect of aortic atresia or
herniation of the foramen ovale valve. Once the lesion
is developed, the right ventricle supplies the lower
body and lungs through the pulmonary trunk, pulmonary
arteries, ductus, and descending aorta. Retrograde
flow with a right-to-left shunt across the transverse
aortic arch supplies the subclavian-innomiate
system and the coronary arteries. This altered flow
pattern may be recognized by careful color flow mapping.
Without surgical intervention the condition is
fatal during neonatal life. Progress in pediatric cardiac
surgery, especially introduction of the Norwood
procedure staged with the Fontan operation [42], has
substantially improved the outcome (Table 33.4). Because
the condition is associated with neonatal crisis
and the staged surgical repair requires prior preparation,
prenatal diagnosis is essential for developing an
appropriate, timely management plan.
Pulmonary Atresia, Intact Ventricular Septum,
Right Heart Hypoplasia Syndrome
Pulmonary atresia with an intact ventricular septum
and right heart hypoplasia is a common variant of
pulmonary atresia/intact ventricular septum syndrome
and is related to the atretic condition of the
tricuspid valve. The latter is associated with underdevelopment
of the right ventricular chamber. In the
absence of atresia, the tricuspid valve is incompetent
and the right ventricular chamber, instead of being
hypoplastic, becomes enlarged. The right atrium
shows varying degrees of hypertrophy and dilation
and often demonstrates a secundum-type septal defect.
Hemodynamic adjustment includes diversion of
flow from the right atrium to the left atrium and retrograde
flow via the ductus into the pulmonary vessels.
Echocardiographic diagnosis, in most cases, can
be performed with relative ease by demonstrating the
diminutive right ventricular cavity with scant or absent
flow (Fig. 33.16). In addition, pulmonary vascular
atresia may be recognized in the long-axis and
arch views. The prognosis without intervention is
Fig. 33.16A, B. B-mode and Color Doppler flow depiction of
hypoplastic left heart. B-mode gray-scale echocardiogram.
A Diminutive left atrium (LA) and left ventricle (LV). This is reconfirmed
by color flow depiction of markedly decreased atrioventricular
flow on the left side. B The right atrium (RA)
and the right ventricle (RV) demonstrate compensatory increase
in size and flow. Flow away from the transducer is
coded in blue and toward the transducer in red
poor, although the outcome has improved with the introduction
of medical management with prostaglandin
to maintain ductal patency and advanced surgical
interventions, such as balloon atrial septostomy and
systemic-to-pulmonary artery anastomosis.
Outflow Tract Anomalies
Tetralogy of Fallot
The tetralogy of Fallot involves a perimembranous
VSD, pulmonic stenosis, aortic root overriding the
ventricular septum, and a hypertrophic right ventricle.
The anomalous development is attributable to