Congenital malformations - Edocr

188 PART V CARDIAC MALFORMATIONS
congenital heart defect. 5 The most common associated
heart defect is a VSD (40–45%), single
or multiple, in various locations in the septum. 5
A malaligned VSD can cause outflow obstruction
to the pulmonary artery. Coronary origin
anomalies are common, however are not clinically
significant. Unlike the other conotruncal
defects discussed in this chapter, TGA is not
commonly associated with an inherited malformation
syndrome, however this lesion is seen
with teratogenic syndromes which are listed in
Table 28-1. Extracardiac anomalies are infrequent,
found in less than 10% of patients. 5
EVALUATION
Suspicion of cyanotic heart disease should be
investigated with a hyperoxia test, chest x-ray,
and ECG. On chest x-ray, the mediastinum is
narrow due to the great arteries projecting in
line in the AP or PA view creating the classic
“egg on a string” cardiac silhouette. Arterial
blood gas will demonstrate low P a O 2 , rarely
above 35 mmHg on room air, and a normal or
mildly elevated P a CO 2 . With 100% oxygen administration,
the increase in P a O 2 directly reflects
the effective size of the shunting lesion. 3
This increase, however, is not significant enough
to pass the hyperoxia test in which the P a O 2 will
typically rise above 100 mmHg after receiving
100% oxygen if cyanosis is caused by pulmonary
disease but the P a O 2 will remain less
than 100 mmHg with less than a 30 mmHg rise
if the cyanosis is due to right to left shunting from
an intracardiac defect. A cardiology consult for
evaluation and possible emergent intervention
should be requested immediately. Echocardiography
alone can confirm the diagnosis. Occasionally
cardiac catheterization with angiography may be
necessary to delineate the coronary artery
anatomy prior to surgical intervention. Because
this is typically an isolated defect, a genetics
evaluation should be reserved for those patients
who appear dysmorphic or have complex TGA.
THERAPY AND PROGNOSIS
If there is no adequate mixing lesion, a balloon
atrial septostomy or Rashkind procedure can be
performed emergently at the bedside under
transthoracic echo guidance. A balloon tipped
catheter is advanced from the inferior venacava
into the right atrium and through the septum
into the left atrium. The balloon is then inflated
and quickly jerked across the septum into the
right atrium. The objective is to tear the septum
creating an unrestricted atrial septal defect.
The surgical repair of choice is the arterial
switch operation. The ascending aorta and main
pulmonary artery are transected above their respective
valves and transposed such that the
morphologic left ventricular outflow is to the
aorta, and right ventricular flow to the pulmonary
artery. The coronary artery origins are
removed from the sinuses of the native aorta
and relocated to the supravalvar neoaortic area.
Complications are mainly related to coronary
compromise and outflow tract obstruction.
Overall, the long-term prognosis is excellent.
GENETIC COUNSELING
The risk of recurrence of TGA is relatively low
at 1.5%. Fetal echocardiography should be performed
with each subsequent pregnancy.
TETRALOGY OF FALLOT
INTRODUCTION
Tetralogy of Fallot (TOF) has four cardinal features;
VSD, pulmonary stenosis, overriding aorta,
and right ventricular hypertrophy. It is the degree
of obstruction of flow to the pulmonary arteries
that determines the clinical and surgical course.
Where TGA represents no rotation of the
great arteries, TOF is an incomplete rotation of
the arteries occurring during the sixth week of
gestation. The truncal division is complete and