Which parameter is used to indicate stenosis at a graft site?

• A. Waveform width
• B. Peak systolic velocity
• C. Focal velocity acceleration
• D. End-diastolic velocity

Answer: (C)

In evaluating a graft for stenosis, the most telling sign is a localized, sharp increase in flow velocity at the narrowed segment—focal velocity acceleration. This means you can identify a discrete point where the velocity rises abruptly as it passes through the constricted area, with velocity then returning to lower values beyond the lesion. This direct localization of a high-velocity jet is what points to a true stenosis.

Other parameters can be affected by graft flow or downstream resistance but are less specific. Peak systolic velocity can be elevated for reasons other than a focal narrowing and doesn’t by itself prove a stenosis. End-diastolic velocity reflects downstream vascular resistance more than the presence of a focal lesion. Waveform width or spectral broadening indicates turbulent flow, which can occur with stenosis but isn’t as definitive as observing a focal acceleration at the lesion. In practice, you’d still compare velocities across segments and may calculate a velocity ratio to quantify stenosis, but focal velocity acceleration is the key indicator of a narrowed graft segment.