High Carotid Velocities with a Contralateral Occlusion: Grading and Communicating

All three primary parameters meet the consensus (SRU) thresholds for a 70–99% stenosis: ICA peak systolic velocity ≥230 cm/s (here 385), end-diastolic velocity ≥100 cm/s (here 155), and ICA/CCA ratio ≥3.2 (here 6.2). Discordance between parameters or an EDV that is disproportionately high should prompt a search for an explanation rather than a guess.

Confounders in this patient:

• Contralateral occlusion produces compensatory high flow in the ipsilateral system, which inflates velocities relative to the anatomical degree of stenosis.
• Anaemia (Hb 10.2) lowers blood viscosity and raises velocity for the same lumen.
• Tachycardia and elevated blood pressure raise cardiac output and flow velocity.
• Incomplete distal visualisation means you cannot assess post-stenotic flow, which is essential for detecting near-occlusion - the situation where a very tight stenosis causes distal collapse and velocities fall rather than rise. A distal ICA velocity lower than the ipsilateral CCA velocity, or a visible string sign, would indicate near-occlusion rather than the 70–99% category, and near-occlusion is managed differently.

So the correct statement is: velocity criteria are met for 70–99%, but they are likely to overestimate the anatomical lesion in this physiological setting, and near-occlusion has not been excluded.

The report should state the category, the parameters used, and the limitations:

• "Right ICA stenosis, 70–99% by NASCET-equivalent velocity criteria (PSV 385 cm/s, EDV 155 cm/s, ratio 6.2)."
• "Distal ICA not fully visualised; near-occlusion not excluded."
• "Velocities may be elevated by contralateral ICA occlusion, anaemia and high cardiac output; anatomical confirmation advised."

Why the method matters. NASCET measured the residual lumen at the narrowest point against the normal distal ICA, while ECST measured against the estimated outer bulb wall. For the same plaque, ECST numbers are systematically higher - a lesion that is 70% by NASCET may be reported as 80–85% by ECST. Mixing the two produces apparent discrepancies between ultrasound, CTA and angiography, and can tip a patient across a treatment threshold. Velocity criteria were validated against NASCET, so report in NASCET terms and state the method.

Given the symptomatic presentation and the incomplete distal view, recommend CTA or MRA for anatomical confirmation rather than proceeding directly on the ultrasound number alone.

This is a critical result in a symptomatic patient. Guideline practice is carotid endarterectomy for a symptomatic 50–99% stenosis, and the benefit falls steeply with delay - the accepted target is intervention within 14 days of the index event, and sooner where services allow. This patient's event was 3 days ago, so the clock is already running.

The communication therefore must be same-day and direct: speak to the referring clinician (or the on-call vascular team if the referrer is unavailable), state the category, state that near-occlusion is not excluded and that anatomical imaging is needed urgently, and record the name, time and content of the conversation in the report. A routine posted report is inadequate.

Practical points:

• Do not simply write "80% as requested" - that attaches a number you cannot defend.
• Do not delay the report while waiting for a confirmatory scan; the referring team needs the finding now.
• If the patient is on best medical therapy only, ensure he has been given secondary prevention advice and that the transient visual loss has been recognised as a warning event rather than an eye problem.