ductus venosus flow assessment

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Fetal ductus venosus flow assessment can be useful in a number of situations in fetal ultrasound:

Of all the pre-cardiac veins, the ductus venosus allows the most accurate interpretation of fetal cardiac function as well as myocardial hemodynamics .

Radiographic assessment

Ultrasound
Technique
  • the fetus should be as still as possible
    • variability in the heights of the S and D waves may indicate fetal breathing, which is normal, but wait for the fetus to be more still before evaluating
  • the probe is ideally focused so sampling is done where the umbilical vein joins the ductus venosus
  • a right ventral mid-sagittal view of the fetal trunk should be obtained and color flow mapping used to demonstrate the umbilical vein, ductus venosus and fetal heart
  • the probe is ideally angled to allow a mid sagittal plane or a transverse oblique plane through the fetal abdomen
  • the image should be magnified enough for the fetal thorax and abdomen to occupy the whole screen
  • do not contaminate the ductus venosus flow with the flow from the fetal inferior vena cava, for this the Doppler sample should be small (0.5-1 mm)
  • the insonation angle should be 30° or less
  • the sweep speed should be high (2-3 cm/s) so that the waveforms are spread allowing better assessment of the A wave 
  • set the wall filter low enough so that the A wave is not obscured

On Doppler ultrasound, the flow in the ductus venosus has a characteristic triphasic waveform where in a normal physiological situation flow should always be in the forward direction (i.e. towards the fetal heart).

This triphasic waveform comprises of:

  • S wave: corresponds to fetal ventricular systolic contraction and is the highest peak
  • D wave: corresponds to fetal early ventricular diastole and is the second highest peak
  • A wave: corresponds to fetal atrial contraction and is the lowest point in the wave form albeit still being in the forward direction
    • as above, reversal of the A wave (i.e. crossing the baseline) is always abnormal

See also

Siehe auch:
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