What is the typical Doppler signal pattern distal to an aortoiliac occlusion?

The characteristic Doppler signal pattern distal to an aortoiliac occlusion is typically low-pitched and monophasic. This pattern occurs due to the significant reduction in blood flow that results from the occlusion. When blood flow is severely compromised, the Doppler waveform loses its triphasic or biphasic components, which are indicative of a healthy, well-perfused artery with normal arterial flow dynamics.

In a normally functioning artery, the triphasic waveform is common, reflecting normal arterial blood flow with high velocities during systole and a return to baseline during diastole. However, in cases of significant stenosis or occlusion, particularly in the aortoiliac region, the waveform changes. The low pitch of the monophasic waveform indicates steady, non-pulsatile flow, which is a result of the distal tissues receiving less blood supply. The absence of the triphasic nature signifies that the vascular resistance has increased, often leading to more laminar flow rather than pulsatile flow associated with healthy arteries.

Overall, the low-pitched monophasic Doppler signal serves as a critical sign for clinicians, indicating possible severe arterial disease and the need for further diagnostic evaluation or intervention.