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a Chapter 31 Doppler Examination of the Fetal Pulmonary Venous Circulation 459
Fig. 31.17. Supracardiac totally anomalous
pulmonary venous connection
(TAPVC). Left: Longitudinal view of the
upper left thorax with a left persistent
superior vena cava (LSVC) with blood
flow is seen with a perfusion toward the
fetal head (in red). Right: In the threevessel
view the pulmonary trunk is antegrade
perfused (blue), and the aorta is
hypoplastic and cannot be seen. On
both sides of the pulmonary trunk the
left persistent (LSVC) and right SVC are
perfused in opposite directions which is
typical for a supracardiac TAPVC
upward toward the upper thorax (Fig. 31.17, left). A
longitudinal visualization of the LVCS may therefore
help enormously (Fig. 31.17, left). Furthermore, blood
flow in the innominate vein appears increased compared
with other conditions, since in addition to
blood coming from the left side of the upper extremity,
blood flow of the lungs will pass through it. Even
by using a cardiac setting of color Doppler with high
velocities, the innominate vein will appear very
clearly with high flow. Pulsed Doppler of pulmonary
veins may be of help in these conditions, especially
in cases with obstruction of these veins.
The supracardiac type of TAPVC connecting directly
to the superior vena cava is difficult to detect
unless the superior vena cava is dilated.
A common feature in both conditions could be the
discrepant size of the right and left heart [25]. In supracardiac
and cardiac TAPVC the left side of the
heart is more narrow due to lack of blood flow to the
left and the right side is dilated due to the increased
flow; therefore, it has to be borne in mind that conditions
suspicious for size discrepancy, such as right
ventricular dysfunction suggesting tricuspid insufficiency
or aortic coarctation, should be suspicious for
supracardiac or cardiac TAPVC as well.
Cardiac TAPVC
In cardiac TAPVC pulmonary veins connect directly
to the coronary sinus, which becomes dilated, or less
commonly the connection is directly into the posterior
wall of the right atrium (Fig. 31.18).
The first condition can be detected when a dilated
coronary sinus is found. Generally, the best plane to
visualize a coronary sinus is a cross section just below
the four-chamber view as we recently described
in an article on normal and abnormally dilated coronary
sinus [26].
The direct connection of pulmonary veins with the
right atrium can be visualized by means of color
Doppler or power Doppler (Fig. 31.19). This is rarely
detected primarily on screening ultrasound but mainly
when there is a suspicious sign. The two clues for
suspicion are either the small size of the left side of
the heart compared with the right or the presence of
right atrial isomerism (asplenia) as detected from
upper abdomen anatomy (juxtaposition of aorta and
inferior vena cava) [24]. In Fig. 31.19 one can recognize
the sampling vein behind the right atrium where
the pulmonary veins drain. Pulsed Doppler demonstrates
the continuous rather than the typical pulsatile
flow.
Fig. 31.18. Cardiac TAPVC. All pulmonary veins are connected
to the right atrium. (Courtesy of Philippe Jeanty
from www.Thefetus.net)