7.3\ Doppler Spectrum

of the Inferior Vena Cava

Fig. 9.28  Doppler spectrum of the inferior vena cava

7.3.1\ Scanning Method

The patient should be in a supine position. The probe is placed vertically to the right of the anterior median line, using the liver as the echo window.

7.3.2\ Section Structure

The Doppler spectrum of the segment proximal to the heart of the IVC is triphasic or quadriphasic; s wave: in the systolic phase of the ventricle, blood flows into the right atrium from the IVC because of the low pressure in the right atrium; v wave: in the isovolume diastolic phase, the pressure in the right atrium increases continuously and the blood flows reversely into the IVC; d wave: in the diastolic phase, the tricuspid valve opens, the pressure in the right atrium decreases, and blood flows into the right atrium from the IVC; a wave: with contraction of the right atrium, blood flows into the IVC; the segment distal to

the heart is not influenced by the contraction of the heart; the pattern of the Doppler spectrum is continuous forward blood flow without a large fluctuation in amplitude.

7.3.3\ Measurement Method and Normal Value

The peak flow velocity is measured, and the direction of the blood flow is determined.

7.3.4\ Clinical Application Value

Continuous single-phase high-velocity turbulence is typical at the stenosis of the vessel. In the case of right heart failure, the diameter of the IVC increases with a decreased periodical spectrum fluctuation. If this is combined with tricuspid insufficiency, there is a reverse s wave during the contraction of the right ventricle. Decreased periodical spectrum fluctuation is also seen in patients with hepatic cirrhosis.