What are the recommendations for carotid endarterectomy based on the North American Symptomatic Carotid Endarterectomy Trial (NASCET)?

NASCET Trial: Recommendations for Carotid Endarterectomy

Core NASCET Findings

Carotid endarterectomy provides substantial benefit for symptomatic patients with 70-99% stenosis, reducing 2-year ipsilateral stroke risk from 26% to 9%, and should be performed within 14 days of symptom onset by surgeons with documented perioperative stroke/death rates <6%. 1, 2, 3

Stenosis Measurement Method

• NASCET established the standard method for measuring carotid stenosis: % stenosis = (1 - [narrowest ICA diameter / diameter of normal distal cervical ICA]) × 100% 1, 4
• This differs from the European ECST method, requiring conversion when comparing studies 1, 5
• Duplex ultrasound criteria for NASCET ≥70% stenosis: ICA peak systolic velocity >210 cm/s OR ICA PSV/CCA PSV ratio >4.0 4, 6

Symptomatic Stenosis: Treatment Thresholds

Severe Stenosis (70-99%)

• NASCET was stopped prematurely at 18 months for this group due to overwhelming benefit of surgery 1
• Absolute risk reduction of 17% at 2 years (9% surgical vs 26% medical) 1, 3
• This benefit persists at 8 years with only 6.7% cumulative stroke/death rate 3
• Surgery must be performed within 14 days of symptom onset, ideally within the first few days once neurologically stable 7, 2
• Approximately 90% of contemporary guidelines endorse CEA as routine treatment for this degree of stenosis 2

Moderate Stenosis (50-69%)

• Surgery provides modest benefit: 5-year ipsilateral stroke risk of 15.7% (surgical) vs 22.2% (medical), requiring treatment of 15 patients to prevent 1 stroke 1, 3
• This benefit is substantially lower than for ≥70% stenosis and requires exceptional surgical skill 7, 3
• Patients require estimated life expectancy >5 years to realize benefit 7
• Women with 50-69% stenosis showed no clear benefit in NASCET 7
• Greatest benefit seen in: men, recent stroke (vs TIA), hemispheric symptoms, age >75 years 3, 8

Mild Stenosis (<50%)

• No benefit from surgery; medical therapy alone is appropriate 5, 3
• Surgery was actually harmful in patients with <30% stenosis 5

Critical Quality Metrics

The surgical team must demonstrate documented perioperative morbidity/mortality rates <6% for symptomatic patients; otherwise medical therapy alone is superior. 7, 2

• The combined 30-day stroke and death rate across NASCET, ECST, and VACS trials was 7.1% 1
• Individual surgeons must audit and quote their own results 2, 8
• A high operative risk eliminates the long-term benefit of surgery 8

CEA vs Carotid Artery Stenting

CEA is preferred over carotid artery stenting for symptomatic patients 7

• CAS may be considered only for patients who are NOT candidates for CEA due to technical, anatomic, or medical reasons 7
• CAS carries higher perioperative stroke risk, particularly in patients >70 years 2
• In CREST trial, symptomatic patients had higher periprocedural stroke rates with CAS (5.5%) vs CEA (3.2%) 7

Mandatory Medical Therapy

Intensive medical therapy is required for ALL patients regardless of whether revascularization is performed: 7, 2

• Antiplatelet agents (aspirin or clopidogrel)
• High-intensity statin therapy targeting LDL <70 mg/dL
• Aggressive blood pressure management
• Diabetes control
• Smoking cessation
• Diet and exercise modifications

Special Considerations

Near-Occlusion ("String Sign")

• Surgery provides NO benefit in patients with near-occlusion despite high-grade stenosis 5, 8
• The effect of surgery in near-occlusion was highly significantly different from 70-99% stenosis without near-occlusion (p=0.002) 5
• Emergency CEA is unnecessary for this finding 8

Timing of Surgery

• Maximum benefit occurs when surgery is performed within 14 days, with diminishing benefit as time from symptom onset increases 7, 2
• Patient must be neurologically stable before proceeding 2

Patient Selection Factors Associated with Greater Benefit

• Male sex 3, 8
• Age >75 years 8
• 90-99% stenosis (without near-occlusion) 8
• Irregular plaque morphology 8
• Hemispheric symptoms (vs retinal) 3, 8
• Recent stroke as qualifying event (vs TIA) 3
• Contralateral carotid occlusion 8

Asymptomatic Stenosis

NASCET specifically studied symptomatic patients; for asymptomatic stenosis ≥60%, surgery may be considered only in highly selected patients with life expectancy >5 years and documented surgical complication rates <3% 2