What is the percentage of stroke risk reduction with carotid endarterectomy (CEA) for patients with symptomatic and asymptomatic carotid artery stenosis?

Stroke Risk Reduction with Carotid Endarterectomy

For symptomatic carotid stenosis ≥70%, carotid endarterectomy provides a 53-65% relative risk reduction in stroke, translating to an absolute risk reduction of approximately 17% at 2 years and 6.5% at 5 years; for asymptomatic stenosis ≥60%, the benefit is substantially smaller with only a 53% relative risk reduction but just 6% absolute risk reduction over 5 years. 1

Symptomatic Carotid Stenosis

Severe Stenosis (70-99%)

The NASCET trial demonstrated the most robust benefit for symptomatic patients with severe stenosis:

• Absolute risk reduction of 17% at 2 years (9% stroke risk with CEA versus 26% with medical therapy alone), representing a 65% relative risk reduction 1
• At 5 years, the ipsilateral stroke rate was 15.7% with CEA versus 22% with medical therapy, yielding an absolute risk reduction of 6.3% 1, 2
• Number needed to treat (NNT) = 6 patients to prevent one stroke over 5 years 1
• The perioperative stroke/death risk was 5.8% in NASCET 1

The benefit is most pronounced when CEA is performed within 2 weeks of the symptomatic event, with significantly diminished benefit when delayed beyond this timeframe 3

Moderate Stenosis (50-69%)

The benefit for moderate symptomatic stenosis is considerably smaller:

• Absolute risk reduction of 4.6-6.5% at 5 years (15.7% with CEA versus 22.2% with medical therapy) 1, 4, 2
• NNT = 15-22 patients to prevent one stroke over 5 years 1, 4
• The perioperative risk was 6.7% at 30 days 1, 2
• CEA is reasonable for select patients in this category, but exceptional surgical skill is mandatory with perioperative complication rates <3% 4, 2

Mild Stenosis (<50%)

CEA provides no benefit for symptomatic stenosis <50%:

• No significant difference in stroke rates between surgical (14.9%) and medical (18.7%) treatment groups (P=0.16) 2
• CEA is not indicated for this degree of stenosis 4

Asymptomatic Carotid Stenosis

Severe Stenosis (60-99%)

The benefit for asymptomatic patients is markedly smaller than for symptomatic patients:

• ACAS trial showed 53% relative risk reduction but only 6% absolute risk reduction over 5 years (5.1% with CEA versus 11% with medical therapy) 1
• NNT = 21 patients to prevent one stroke over 5 years 5
• The combined perioperative angiography and surgical risk was 2.7% (1.2% angiography risk + 1.5% surgical risk) 1
• ACST trial demonstrated similar results: 5-year stroke rates of 6.4% with early surgery versus 11.7% with medical management, representing an absolute risk reduction of 5.3% 1

Critical considerations for asymptomatic stenosis:

• The benefit only accrues after 1-2 years, meaning patients must survive the perioperative period before realizing any advantage 1
• Women appeared to benefit less than men (17% non-significant risk reduction in women versus 66% in men), partly due to higher perioperative complication rates in women (3.6% versus 1.7%) 1
• Perioperative complication rates must be <3% for the benefit to outweigh the risk 4, 5
• Life expectancy must be at least 5 years for patients to realize the benefit 5

Contemporary Context

Recent evidence suggests the benefit of CEA for asymptomatic stenosis may be even smaller in the modern era:

• The 60-70% decline in stroke rates among medically treated patients from 1995-2010 has narrowed the treatment gap 6
• CREST-2 showed no significant benefit of CEA over intensive medical management alone (P=0.24) for asymptomatic stenosis 6
• A 2012 meta-analysis found CEA did not significantly affect stroke/death risk for asymptomatic patients (RR=0.93; 95% CI, 0.84-1.02; P=0.14) 7
• Modern medical therapy with high-intensity statins, antiplatelet agents, and aggressive risk factor control has substantially improved outcomes without surgery 6

Key Clinical Pitfalls

Failing to distinguish symptomatic from asymptomatic patients is a critical error, as the risk-benefit ratio differs substantially between these populations 3

Not recognizing the critical timing window for symptomatic patients leads to suboptimal outcomes, as benefit is maximal within 2 weeks of the index event 3

Proceeding with CEA when perioperative complication rates exceed 3% negates the benefit, particularly for asymptomatic patients 1, 4, 5

Ignoring sex-based differences in outcomes, particularly the higher perioperative risk in women, can lead to inappropriate patient selection 1