Extracranial-Intracranial Bypass Surgery for Stroke Prevention in Hemodynamic Cerebral Ischemia: The Carotid Occlusion Surgery Study Randomized Trial

Study Questions:

What is the benefit of bypass surgery for patients with symptomatic atherosclerotic internal carotid artery occlusion (AICAO) and hemodynamic cerebral ischemia?


The authors performed a parallel-group, randomized, open-label, blinded-adjudication clinical treatment trial at 49 centers in the United States and Canada from 2002-2010. A total of 195 patients with arteriographically confirmed AICAO causing hemispheric symptoms within 120 days and hemodynamic cerebral ischemia identified by ipsilateral increased oxygen extraction fraction measured by positron emisson tomography (PET) were randomized to receive surgery (n = 97) or best medical therapy (n = 98). The primary endpoint was the occurrence of all stroke and death from surgery (for the surgery arm) or from randomization (medical therapy arm) plus 30 days and any ipsilateral ischemic stroke within 2 years of randomization. All patients were followed up for the primary endpoint occurrence, or end of 2 years or termination of the trial.


The trial was terminated early for futility. There was no difference in the 2-year primary endpoint between the two arms (21% for the surgical arm vs. 22.7% for the medical therapy arm; p = 0.78). Thirty-day rates for ipsilateral ischemic stroke were higher in the surgery arm (14.4% vs. 2.0%). No difference in any secondary endpoints was observed.


The authors concluded that external carotid to internal carotid bypass surgery was not associated with any reduction in ipsilateral stroke compared with medical therapy alone in patients with recently symptomatic AICAO and hemodynamic cerebral ischemia.


Symptomatic AICAO is a relatively rare condition, and is associated with a high risk of stroke. The results of this study suggest that surgery is associated with a higher risk of periprocedural stroke with a subsequent lowering in downstream stroke risk; but overall, there was no difference between patients undergoing surgery or those treated medically. An endovascular approach has been successfully used in select centers with an acceptable complication rate (Circ Cardiovasc Interv 2008;1:119-25), and further studies are warranted to assess if this is associated with better outcomes compared with medical therapy only.

Clinical Topics: Vascular Medicine

Keywords: Stroke, Canada, Carotid Artery Diseases, Brain Ischemia

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