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Chapter 31
Doppler Examination
of the Fetal Pulmonary Venous Circulation
Rabih Chaoui, Franka Lenz, Kai-Sven Heling
Introduction
The assessment of the pulmonary venous system in
the fetus has evolved dramatically in the past decade
due to the routine use of spectral and color Doppler
ultrasound. Besides checking the normal connection
of pulmonary veins during fetal echocardiography,
the interest in these veins has increased recently in
order to get insight into the mystery of the pulmonary
circulation in the human fetus in vivo. Physiologic
conditions and changes during pregnancy have
been assessed and have allowed the comparison with
data under abnormal conditions. This chapter briefly
reviews the clinical value of Doppler assessment of
pulmonary veins.
Visualization of Pulmonary Veins
Using Real-Time and Color Doppler
Ultrasound
There are four pulmonary veins, inferior and superior
on the right and left sides. All these veins enter the left
atrium separately and have their own ostium. Using
high-resolution real-time equipment and a perpendicular
approach to the site of connection, the echolucent
veins may then be recognizable in the surrounding
gray lung (Fig. 31.1). It is generally difficult to visualize
all four pulmonary veins in the fetus, but in the fourchamber
view the two inferior veins can be visualized.
Pulmonary veins in the fetus have a diameter of approximately
1 mm or less and are therefore difficult
to identify routinely on screening ultrasound. This is
also the reason why pulmonary volume flow is analyzed
quantitatively on the arterial side.
In our examination technique we seek one right pulmonary
vein (inferior) along a fictive line prolonging
the intra-atrial septum. In real-time this is best visualized
from the right transverse or slight dorsoanterior
approach (Fig. 31.1). Using color Doppler this vein
can be visualized either by an apical approach when
(red) flow is seen toward the left atrium at the site
where the inter-atrial septum inserts (Fig. 31.2) or by
a dorsoanterior approach (flow in blue; Fig. 31.3).
The left pulmonary vein (inferior) is found as a
vessel directly pointing toward the foramen ovale flap
(Figs. 31.4, 31.5). It can be visualized in real-time
when the heart is examined from the left transverse
side (Fig. 31.4). Using color Doppler the same plane
can be used to visualize flow in blue (Fig. 31.4), or a
transverse right side to visualize blood flow in red toward
the transducer (Figs. 31.2, 31.5). An apical
approach slightly more from the right thoracic side
may allow the visualization of two veins from the
right and the left coursing into the left atrium (Fig.
31.2). New color Doppler techniques, such as power
Doppler ultrasound or dynamic flow, can be very
helpful tools in visualizing pulmonary veins especially
when insonation angle is more perpendicular to the
vessels of interest (Fig. 31.6).
Real-time visualization of the pulmonary veins was
facilitated in the past few years by using new contrasting
techniques, such as harmonic imaging or
compound imaging (SonoCT, CRI, etc.; Figs. 31.1,
Fig. 31.1. Third-trimester fetus in dorsoanterior position.
One right pulmonary vein (RPV) is visualized as the prolongation
of the intraatrial septum. In this case we used harmonics
imaging and a 5-MHz transducer. RA right atrium,
LA left atrium