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ACAS

Endarterectomy for Asymptomatic Carotid Artery Stenosis

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Year of Publication: 1995

Authors: Executive Committee for the Asymptomatic Carotid Atherosclerosis Study

Journal: JAMA

Citation: JAMA. 1995;273:1421-1428

Link: https://pubmed.ncbi.nlm.nih.gov/7723155

PDF: https://www.urmc.rochester.edu/MediaLibr...uments/ACAS.pdf

Clinical Question

Will carotid endarterectomy added to aggressive reduction of modifiable risk factors and administration of aspirin reduce the 5-year risk of ipsilateral cerebral infarction in individuals with asymptomatic hemodynamically significant carotid artery stenosis?

Bottom Line

Patients with asymptomatic carotid artery stenosis of 60% or greater reduction in diameter and whose general health makes them good candidates for elective surgery will have a reduced 5-year risk of ipsilateral stroke if carotid endarterectomy performed with less than 3% perioperative morbidity and mortality is added to aggressive management of modifiable risk factors

        Major Points
        Prospective, randomized, multicenter trial with 1659 patients with asymptomatic carotid stenosis ≥60%
Median follow-up of 2.7 years with 4657 patient-years of observation
53% relative risk reduction in ipsilateral stroke and perioperative stroke/death (5.1% vs 11.0%)
Absolute 5-year risk reduction of 5.9%, number needed to treat of 17
Perioperative stroke/death rate of 2.3% in surgical group vs 0.4% in medical group
Trial stopped early after eighth interim analysis due to efficacy

      

Design

Study Type: Randomized controlled trial

Randomization: 1

Blinding: Masked outcome assessment with blinded adjudication committee for end points

Enrollment Period: December 1987 to December 1993

Follow-up Duration: Median 2.7 years

Centers: 39

Countries: United States, Canada

Sample Size: 1659

Analysis: Intention-to-treat analysis using Kaplan-Meier estimates with large-sample tests, modified O'Brien-Fleming stopping rule

Inclusion Criteria

Age between 40 and 79 years
Asymptomatic carotid artery stenosis ≥60% diameter reduction
Patient accessibility and willingness to be followed for 5 years
Valid informed consent
Compatible history and findings on physical and neurological examinations

Exclusion Criteria

Cerebrovascular events in distribution of study carotid artery or vertebrobasilar system
Symptoms referable to contralateral cerebral hemisphere within previous 45 days
Contraindication to aspirin therapy
Disorder that could seriously complicate surgery
Condition likely to produce disability or death within 5 years

Baseline Characteristics

Characteristic	Control	Active
Mean age	67 years	67 years
Male sex	66%	66%
White race	95%	94%
Mean weight	67 kg (women), 81 kg (men)	67 kg (women), 81 kg (men)
Mean systolic BP	146 mm Hg	146 mm Hg
Mean diastolic BP	78 mm Hg	78 mm Hg
Mean cholesterol	5.90 mmol/L (228 mg/dL)	5.90 mmol/L (228 mg/dL)
Hypertension	64%	64%
Diabetes	21%	25%
Current smokers	24%	28%
Prior MI	21%	21%
Ipsilateral bruit	74%	76%

Arms

Field	Surgical Group	Control
Intervention	Carotid endarterectomy within 2 weeks of randomization plus daily aspirin (325 mg) and medical risk factor management	Daily aspirin (325 mg) and aggressive medical risk factor management including hypertension control, diabetes management, lipid control, smoking cessation
Duration	5 years follow-up	5 years follow-up

Outcomes

Outcome	Type	Control	Intervention	HR / OR / RR	P-value
Ipsilateral stroke and any perioperative stroke or death	Primary	92 (11.0%)	42 (5.1%)	5.90%	0.004
Major ipsilateral stroke or perioperative major stroke/death	Secondary	50 (6.0%)	28 (3.4%)	0.43 (-0.17 to 0.72)	0.12
Any stroke or perioperative death	Secondary	146 (17.5%)	102 (12.4%)	0.29 (-0.05 to 0.52)	0.09
Any stroke or death	Secondary	266 (31.9%)	211 (25.6%)	0.20 (-0.02 to 0.37)	0.08
Perioperative stroke or death	Adverse	3 (0.4%)	19 (2.3%)
Arteriographic complications	Adverse	0	5 (1.2% of those undergoing angiography)

Subgroup Analysis

Men showed 66% risk reduction (95% CI 36% to 82%) while women showed 17% reduction (95% CI -96% to 65%), but difference not statistically significant (P=0.10)

Criticisms

Only 15% of screened stroke patients were enrolled, limiting generalizability
Higher perioperative complication rate in women (3.6% vs 1.7% in men)
Trial stopped early based on interim analysis
Median follow-up only 2.7 years with limited 5-year data
All surgical patients required arteriography with additional 1.2% stroke risk
Results may not apply to centers with higher perioperative complication rates

Funding

National Institute of Neurological Disorders and Stroke, US Public Health Service

Based on: ACAS (JAMA, 1995)