Which velocity parameter is most commonly used to assess ICA stenosis?

• A. End-diastolic velocity
• B. Peak systolic velocity
• C. Resistive index
• D. Time-averaged velocity

Answer: (B)

The main idea is that peak systolic velocity in the internal carotid artery is the most reliable single measure for grading stenosis. As the artery narrows, the blood must accelerate to maintain flow, so the highest velocity during heart contraction rises in proportion to how narrowed the vessel is. That makes peak systolic velocity highly sensitive and reproducible for estimating stenosis severity, and it’s the velocity parameter most commonly used in diagnostic criteria (often alongside the ICA/CCA velocity ratio).

End-diastolic velocity can be influenced by downstream resistance and collateral flow, so it doesn’t track stenosis as directly. The resistive index depends on both PSV and EDV and isn’t specific to the degree of narrowing. Time-averaged velocity smooths the waveform and can obscure the peak change that indicates stenosis.