o_1977r8vv9vk1ts2ms0kd8pksa.pdf

454 R. Chaoui et al.
Fig. 31.7. Spectral Doppler of a pulmonary
vein with a triphasic envelope
characterized by the systolic (S) and diastolic
(D) waves, and the A-wave as nadir
during the atrial contraction
Fig. 31.9. Reference range (individual values, mean and
95% data intervals) for peak systolic velocity in the pulmonary
veins plotted against gestational age. (From [9])
Fig. 31.8. A 13-week fetus examined transvaginally with visualization
of a right pulmonary vein (RPV) entering the
left atrium (LA). In a previous pregnancy there was a right
isomerism with totally anomalous pulmonary venous connection
The fetal pulmonary vein velocity waveform is
therefore very similar to that of the venous duct, with
a forward triphasic flow throughout the heart cycle
(Fig. 31.7). Parameters of blood flow velocity waveforms
have been examined in several studies in recent
years and similar results were reported [8±11]. Peak
systolic (Fig. 31.9), diastolic velocities (Fig. 31.10),
and time velocity integral (TVI) increase significantly
during the second half of pregnancy, whereas pulsatility
index decreases (Fig. 31.11) [9]. The rise in