Which duplex waveform pattern most strongly suggests moderate to severe arterial disease?

• A. Triphasic or multiphasic with sharp systolic upstroke
• B. Dampened biphasic with reduced diastolic flow
• C. Monophasic waveform with reduced or absent diastolic flow
• D. Normal triphasic flow with high velocity

Answer: (C)

The key idea is that waveform shape in peripheral arteries reflects how much resistance and perfusion the downstream bed has. In a healthy artery, the duplex spectrum is triphasic or multiphasic with a sharp systolic upstroke, a brief reversal flow, and forward diastolic flow—this shows normal arterial compliance and good downstream perfusion. When disease narrows or occludes the vessel, or when downstream resistance rises, the diastolic component diminishes. The waveform becomes damped and eventually monophasic, with reduced or absent diastolic flow. That monophasic pattern is the strongest signal of moderate to severe arterial disease because it directly indicates a loss of diastolic flow and overall reduced perfusion due to substantial downstream obstruction.

Triphasic or multiphasic with a sharp upstroke is essentially normal. Dampened biphasic with some diastolic flow shows some remaining forward diastolic component and thus less severe disease. Normal triphasic with high velocity can occur at a focal stenosis but doesn’t by itself define moderate to severe diffuse disease.