Risk of stroke from new carotid artery occlusion in the Asymptomatic Carotid Surgery Trial-1
Anne G den Hartog1, Alison W Halliday, Elizabeth Hayter
1Department of Vascular Surgery, UMC Utrecht, Utrecht, The Netherlands.
Insights
New carotid artery occlusions are uncommon after surgery, but increase stroke risk. Patients with severe stenosis (≥70%) face higher risks of occlusion and stroke, especially if untreated.
Area of Science:
- Vascular Surgery
- Neurology
- Clinical Trials
Background:
- The Asymptomatic Carotid Surgery Trial-1 (ACST-1) investigated carotid endarterectomy for asymptomatic carotid stenosis.
- Previous findings indicated reduced stroke risk with surgery in younger patients.
Purpose of the Study:
- To assess the long-term risk of new carotid artery occlusion and associated stroke during ACST-1 follow-up.
- To identify risk factors for developing new occlusions and subsequent strokes.
Main Methods:
- Kaplan-Meier analysis estimated occlusion and stroke risk in patients with existing occlusion.
- Cox proportional hazard regression models identified risk factors for new occlusion and stroke.
- Patients with contralateral occlusion or incomplete follow-up were excluded.
Main Results:
- New occlusions occurred in 1.1% per year, more frequently in untreated, tight stenoses.
- Stroke risk at 10 years was 15.5%, significantly increasing to 20.8% in patients with new occlusions.
- Developing an occlusion independently increased stroke risk (HR 1.78).
Conclusions:
- New carotid artery occlusions were infrequent following carotid endarterectomy in ACST-1.
- Patients with ≥70% stenosis, particularly those not operated on, had higher rates of occlusion and stroke.
- Carotid artery occlusion is an independent prognostic factor for stroke.
Background And Purpose:
In the Asymptomatic Carotid Surgery Trial-1 (ACST-1), 3120 patients with tight asymptomatic carotid stenosis were randomly assigned to medical treatment alone or to carotid endarterectomy and appropriate medication. Successful carotid endarterectomy significantly reduced 10-year stroke risk in younger patients. This study was undertaken to determine the risk of new occlusion and stroke during trial follow-up.
Methods:
Patients with contralateral occlusion at trial entry (n=276) or incomplete duplex follow-up (n=137) were excluded. Risk of occlusion and stroke in patients with occlusion was estimated by Kaplan-Meier analysis. Cox proportional hazard regression models were used to determine risk factors for developing new occlusion and stroke.
Results:
Median follow-up in 2707 patients was 80.0 months (interquartile range, 52.0-115.0). New occlusions occurred in 197 patients (1.1% per annum) but were more likely to occur in arteries with tight stenosis and in unoperated patients. Overall risk of stroke was 7.6% (95% confidence interval [CI], 6.6-8.7) and 15.5% (95% CI, 13.6-17.4) at 5 and 10 years, respectively; for patients with new occlusion, this significantly increased to 17.0% (95% CI, 11.6-22.4) and 20.8% (95% CI, 14.1-26.2), respectively (P<0.001). Stroke was significantly more likely to occur in patients developing occlusion (hazard ratio, 1.78; 95% CI, 1.26-2.51) irrespective of allocated treatment.
Conclusions:
New occlusions were uncommon after carotid endarterectomy in ACST-1. During long-term follow-up, occlusion and stroke were commoner among patients with ≥ 70% stenosis, most of whom had not undergone carotid endarterectomy. Occlusion was an independent prognostic risk factor for occurrence of stroke.
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