What type of waveform proximal to a high-grade stenosis or occlusion would you expect?

• A. Low resistance triphasic
• B. Continuous forward flow
• C. High resistant, sharp peak with no end diastolic flow
• D. Pulsatile with forward diastolic flow

Answer: (C)

The main idea is that waveform shape reflects downstream resistance. Proximal to a high-grade stenosis or occlusion, the downstream bed presents very high impedance, so the upstream artery shows a high-resistance pattern: the systolic upstroke is sharp and the waveform has little to no diastolic flow. In other words, you get a rapid, tall systolic peak with absent end-diastolic flow because the downstream obstruction suppresses diastolic forward movement. Continuous forward flow would imply low downstream resistance, and a pulsatile waveform with forward diastolic flow suggests normal or moderate resistance, not the high resistance seen with a severe downstream lesion.