Ductus venosus

A number of sites have been used to assess venous return to the fetal heart. Waveform indices vary substantially in the inferior vena cava, depending on the sampling site, and the ductus venosus (DV) has emerged as the most clinically useful vessel. The DV originates from the intrahepatic portion of the umbilical vein (UV) and allows shunting of oxygenated blood to the left side of the heart via the foramen ovale. In an oblique transverse section of the fetal abdomen the DV can be identified readily using color Doppler. The higher velocities, due to the narrow lumen of the DV, frequently lead to aliasing, which facilitates identification. The sampling gate should be sufficiently wide to ensure peak velocities are captured but not confined to the proximal section of the DV where a right atrial

Reversed Ductus Venosus Waveform

Figure 32.1 Uterine artery, fetal arterial and venous waveforms. Flow velocity waveforms from the uterine artery (a, b), umbilical artery (c, d), middle cerebral artery (e, f) and ductus venosus (g, h). Panel (a) illustrates a normal uterine artery waveform while Panel (b) shows an abnormal waveform with reduced end-diastolic velocities (EDV) and marked early diastolic notching (arrow). Panel (c) illustrates a normal umbilical artery Doppler waveform with high EDV. In contrast Panel (d) shows the most extreme abnormality with reversal of EDV (arrow). Panel (e) illustrates a normal middle cerebral artery Doppler waveform with relatively low EDV. An example of ''brain sparing'' is shown in Panel (f) with markedly elevated EDV (arrow). Panel (g) illustrates a normal biphasic waveform from the ductus venosus. A severely abnormal ductus waveform is shown in Panel (h) with reversal of the ''a'' wave (arrow).

Figure 32.1 Uterine artery, fetal arterial and venous waveforms. Flow velocity waveforms from the uterine artery (a, b), umbilical artery (c, d), middle cerebral artery (e, f) and ductus venosus (g, h). Panel (a) illustrates a normal uterine artery waveform while Panel (b) shows an abnormal waveform with reduced end-diastolic velocities (EDV) and marked early diastolic notching (arrow). Panel (c) illustrates a normal umbilical artery Doppler waveform with high EDV. In contrast Panel (d) shows the most extreme abnormality with reversal of EDV (arrow). Panel (e) illustrates a normal middle cerebral artery Doppler waveform with relatively low EDV. An example of ''brain sparing'' is shown in Panel (f) with markedly elevated EDV (arrow). Panel (g) illustrates a normal biphasic waveform from the ductus venosus. A severely abnormal ductus waveform is shown in Panel (h) with reversal of the ''a'' wave (arrow).

pattern predominates. Care is also necessary to avoid nearby hepatic veins.

The DV FVW is biphasic with the first peak concomitant with ventricular systole and a second peak in late diastole concomitant with atrial systole (the ''a'' wave). Various indices have been used to describe venous waveforms but the pulsatility index for veins (PIV) is probably the most widely used. The PIV measures the degree of venous pulsatility, using the same ratio as PI in arterial vessels, but allows for reverse flow during diastole. The 95th centile for PIV falls from around 0.9 at 20 weeks to 0.7 at term, with values above this being regarded as abnormal (Hecher et al., 1994). As with the UA, absence or reversal of atrial systolic forward flow (Figure 32.1) are of particular clinical significance (Baschat et al., 2003).

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Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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