🩻 Carotid Stenosis (NASCET / ECST)
Compute extracranial carotid (ICA) stenosis from diameters using the NASCET method (optional ECST) with grade and management direction.
Exclude near-occlusion (distal collapse/string sign) first — the method does not apply.
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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
Worked calculation
The values below come from this tool's own example placeholders and are computed server-side with the formula shown on this page, so the arithmetic can be checked quickly. It demonstrates how to substitute values only — it is not clinical advice and not a real case.
| Narrowest residual lumen A | 1.5 mm |
|---|---|
| Distal normal ICA diameter B (NASCET reference) | 5.0 mm |
| Estimated original bulb diameter C (ECST, optional) | 8.0 mm |
| Clinical context | Symptomatic (ipsilateral TIA/stroke/amaurosis within 6 mo) |
→NASCET stenosis70% · Severe (≥ 70%)
- NASCET：(1 − A/B)×100 = (1 − 1.5/5)×100 = 70%
- ECST：(1 − A/C)×100 = 81% (C = estimated original bulb diameter; ECST usually exceeds NASCET, ~ 70% NASCET ≈ 78% ECST)
- Grade：Severe (≥ 70%) (NASCET method: mild < 50%, moderate 50–69%, severe ≥ 70%)
Frequently asked questions
- What is Carotid Stenosis (NASCET / ECST)?
- Compute extracranial carotid (ICA) stenosis from diameters using the NASCET method (optional ECST) with grade and management direction.
- How is Carotid Stenosis (NASCET / ECST) calculated? What is the core formula?
- 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).
- When is Carotid Stenosis (NASCET / ECST) used?
- Quantify carotid stenosis for revascularization decisions in symptomatic and asymptomatic disease.
- What are the key clinical points for Carotid Stenosis (NASCET / ECST)?
- 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.
- What are the limits and cautions when using Carotid Stenosis (NASCET / ECST)?
- For licensed clinicians and clinical researchers. Interpret results with history, investigations and local protocols; not a diagnosis or prescription, and not a substitute for multidisciplinary decision-making or local guidelines.
- How is Carotid Stenosis (NASCET / ECST) calculated in practice? Can you show a worked example?
- Inputs: Narrowest residual lumen A 1.5 mm, Distal normal ICA diameter B (NASCET reference) 5.0 mm, Estimated original bulb diameter C (ECST, optional) 8.0 mm, Clinical context Symptomatic (ipsilateral TIA/stroke/amaurosis within 6 mo) → Result: NASCET stenosis 70 % · Severe (≥ 70%)（NASCET: (1 − A/B)×100 = (1 − 1.5/5)×100 = 70%, ECST: (1 − A/C)×100 = 81% (C = estimated original bulb diameter; ECST usually exceeds NASCET, ~ 70% NASCET ≈ 78% ECST), Grade: Severe (≥ 70%) (NASCET method: mild < 50%, moderate 50–69%, severe ≥ 70%)）