🩻 Carotid Stenosis (NASCET / ECST)
Compute extracranial carotid (ICA) stenosis from diameters using the NASCET method (optional ECST) with grade and management direction.
Carotid Stenosis (NASCET / ECST)
Narrowest residual lumen A (mm)
Distal normal ICA diameter B (NASCET reference) (mm)
Estimated original bulb diameter C (ECST, optional) (mm)
Clinical context
When to use
Quantify carotid stenosis for revascularization decisions in symptomatic and asymptomatic disease.
How it works
NASCET = (1 − A/B)×100, where A = narrowest residual lumen and B = distal normal ICA diameter. Mild < 50%, moderate 50–69%, severe ≥ 70%. ECST = (1 − A/C)×100 (C = original bulb diameter).
Key points
- Exclude near-occlusion (distal collapse/string sign) first — the method does not apply.
- Symptomatic ≥ 50% usually warrants early evaluation for revascularization (CEA often preferred).
- For extracranial ICA only — not intracranial (use WASID), CCA/ECA or in-stent restenosis.
References
Decision support for licensed clinicians only; not a substitute for clinical judgement, diagnosis or local protocols.