o_1977r8vv9vk1ts2ms0kd8pksa.pdf

550 J. C. Huhta et al.
presence of an increase in reversal of blood velocity
during atrial contraction suggests a state of fetal congestive
heart failure [10, 11].
Pulmonary Veins
Pulmonary venous waveforms are similar to systemic
venous (IVC) waveforms. Reversal in this site could
indicate A-V valvar regurgitation, myocardial failure,
or an obstruction to emptying the atrium.
Pulmonary Artery
Fetal pulmonary resistance is high, and a typical waveform
in the left pulmonary artery reflects this state
with biphasic forward flow: midsystolic reversal and
brief reversal during early diastole. The end-diastolic
velocity at this site is useful for evaluating the state
of the fetal pulmonary vasculature. The normal finding
is low velocity of forward flow into the pulmonary vascular
bed. This flow is of markedly low velocity and
may not be detectable using standard high-pass filter
settings on the current equipment. Absence of this flow
or the finding of reversal of flow during diastole suggests
abnormal peripheral vascular impedance.
Fetal Ductal Evaluation
An Acuson 128 scanner, in combination with 5.0- and
3.5-MHz probes, is used for the fetal cardiovascular
examination. After evaluation of the cardiac anatomy,
continuous-wave Doppler interrogation of the flow
through the ductus arteriosus is performed using 5.0-
or 3.5-MHz image-directed continuous-wave Doppler
sonography in a sagittal plane showing the pulmonary
artery, ductus arteriosus, and descending aorta
simultaneously as previously described [1]. Power
output is kept below 100 mW/cm 2 spatial peak temporal
average at all times. Each study is recorded on
standard VHS 0.5-inch video tape for later analysis,
although on-line analysis of the waveform of the
blood velocity of the ductus is performed for immediate
clinical reporting (pulsatility index). All
Doppler recordings are obtained in the absence of fetal
breathing movements at an angle of less than 308
to flow, and color flow mapping is used for alignment
of the Doppler beam. Waveforms are analyzed for
maximal, end-diastolic, and mean velocities, respectively.
The PI is calculated using the formula: (maximal
velocity ± end-diastolic velocity)/mean velocity,
Fig. 37.1. Doppler waveforms in the
fetal ductus arteriosus. Top: Normal
waveform at 28 weeks shows a systolic
velocity of approximately 1 m/s. Middle:
During terbutaline administration
to the mother, fetal Doppler sonography
of the ductus shows increased
peak velocity with little change in the
end-diastolic velocity resulting in an
increase in the pulsatility index (PI).
Bottom: Fetal ductal constriction shows
increased systolic and diastolic velocities
and a decreased PI. (Reprinted
from [13] with permission)