NASCET · Vascular
Sistemas/Vascular

NASCET NASCET carotid stenosis measurement

vigente

Quantifies internal carotid artery stenosis severity.

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Escala de categorias
<50%50-69%70-99%occlusion

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Procedência e vigência

Órgão emissor
NASCET investigators
Versão
1991
Ano
1991
Família
léxico
Tipo de lógica
flat
Modalidade
CT, MRI, US
Fonte primária
Beneficial effect of carotid endarterectomy in symptomatic patients with high-grade stenosis (NASCET) · doi:10.1056/NEJM199108153250701
Última verificação
2026-06-22
Última checagem
2026-06-22

Lógica de decisão

Forma estruturada (flat). Uma futura calculadora a lê; as categorias abaixo são a superfície legível.

Mostrar a lógica estruturada (JSON)
{
  "categories": [
    "<50%",
    "50-69%",
    "70-99%",
    "occlusion"
  ]
}

Categorias num relance

Cat.SignificadoCondutaRiscoFonte
<50%
Mild stenosis
Mild internal carotid artery stenosis by the NASCET method — a NASCET-derived diameter reduction of 0-49%. NASCET quantifies stenosis by comparing the narrowest residual luminal diameter at the stenosis to the diameter of the normal distal cervical internal carotid artery (ICA) well beyond the bulb, where the walls are parallel and unaffected by plaque: percent stenosis = (1 - [minimal residual luminal diameter / diameter of normal distal ICA]) x 100. In the trial this band gained no significant benefit from carotid endarterectomy.
In symptomatic patients this degree of stenosis was found to derive no significant benefit from carotid endarterectomy (medical/best-medical management).
Severity band from ESCR consensus (PMC9889495), 'Quantifying the degree of stenosis': 'According to NASCET, luminal stenosis is classified as "mild" (0-49%), "moderate" (50-69%), and "severe" (70-99%).' NASCET formula/measurement points from same section and from Wikipedia 'Carotid artery stenosis' Diagnosis section (percent stenosis = (1 - minimum diameter within stenosis / poststenotic diameter) x 100). 'No benefit <50%' from StatPearls 'Carotid Endarterectomy' (NBK470582), Indications section.
50-69%
Moderate stenosis
Moderate internal carotid artery stenosis by the NASCET method — a NASCET-derived diameter reduction of 50-69% (measured by the same residual-lumen-vs-normal-distal-ICA ratio described for the <50% band).
Symptomatic patients with 50% or more ipsilateral stenosis plus a history of ipsilateral stroke or TIA are, per practice guidelines derived from NASCET, candidates for carotid endarterectomy; benefit in the moderate (50-69%) group is smaller than in the severe group.
Severity band from ESCR consensus (PMC9889495), 'Quantifying the degree of stenosis' ('moderate' = 50-69%). CEA recommendation for >=50% symptomatic stenosis from StatPearls 'Carotid Endarterectomy' (NBK470582), Indications section.
70-99%
Severe stenosis
Severe internal carotid artery stenosis by the NASCET method — a NASCET-derived diameter reduction of 70-99% (the residual lumen is reduced to little more than a thread relative to the normal distal ICA). This is the high-grade stenotic-but-still-patent band, short of complete occlusion.
Symptomatic 70-99% stenosis showed the greatest benefit from carotid endarterectomy in NASCET, establishing the 70% threshold as a key indication for surgery in symptomatic patients.
Severity band from ESCR consensus (PMC9889495), 'Quantifying the degree of stenosis' ('severe' = 70-99%). Benefit of CEA for severe (70-99%) symptomatic stenosis from StatPearls 'Carotid Endarterectomy' (NBK470582), Indications section, and corroborated by Wikipedia 'Carotid artery stenosis'.
occlusion
Near occlusion or occlusion
Complete (100%) occlusion of the internal carotid artery — there is no residual lumen, so a NASCET percent-stenosis ratio cannot be meaningfully computed (NASCET treated near-occlusion/occlusion as a distinct category rather than calculating a percentage). Distinct from the patent 70-99% severe band.
Occlusion (100%) / near-occlusion handled as a distinct category beyond the calculable bands per ESCR consensus (PMC9889495), Table 1 categories 'Near-occlusion'/'Occlusion'; near-occlusion-not-calculated point corroborated by NASCET-method discussion (Wikipedia 'Carotid artery stenosis' and NASCET Group commentary that a percent is not calculated for near-occlusion).

Histórico de versões

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NASCET. NASCET carotid stenosis measurement. RadCommons