Where will tardus parvus waveforms be obtained?

• A. Proximal to a stenosis
• B. Distal to a hemodynamically significant stenosis
• C. In the iliac artery
• D. In the superficial veins

Answer: (B)

Tardus parvus reflects a delayed, damped systolic upstroke in the arterial downstream waveform caused by an upstream significant narrowing. When a high-grade stenosis sits in a vessel, the rapid acceleration of blood during systole is obstructed, so the flow distal to the blockage cannot reach a high, sharp peak quickly. The result is a slower rise (tardus) and a lower peak velocity (parvus) in the Doppler signal obtained downstream. Therefore, you would observe tardus parvus waveforms distal to a hemodynamically significant stenosis, in the arterial tree beyond the narrowed segment. It is not expected upstream of the lesion, and it does not occur in veins, which have a different flow pattern.