Impaired cerebral autoregulation distal to carotid stenosis/occlusion is associated with increased risk of stroke at cardiac surgery with cardiopulmonary bypass

Objectives: Severe carotid stenosis and occlusion are associated with an increased risk of stroke during and after cardiac surgery with cardiopulmonary bypass. Relevance of an impaired cerebral autoregulation caused by stenosis/occlusion is unknown. Methods: We prospectively assessed the incidence of stroke in relation to severity of carotid disease and corresponding autoregulatory reserve in 2797 patients who had coronary artery bypass graft and/or valve surgery with cardiopulmonary bypass. Patients underwent preoperative carotid sonography and, in case of severe extracranial disease, transcranial Doppler sonography with carbon dioxide stimulation to assess cerebrovascular reserve capacity. Results: Sixty-seven ( 2.4%) patients had an ischemic stroke, which was fatal in 5. Anterior hemispheric stroke occurred in 42 ( 1.9%) patients with no/low-grade stenosis, 6 ( 1.8%) with medium-grade stenosis, 1 ( 0.6%) with high-grade stenosis/occlusion and normal autoregulation, and 3 ( 27.3%) with high-grade stenosis/occlusion and exhausted autoregulatory reserve. Increased risk was observed in patients with high-grade stenosis/occlusion and exhausted autoregulatory reserve also after adjustment for potential confounders ( adjusted odds ratio [ OR] 28.3, 95% confidence interval [ CI] 5.8-139.1). Stroke risk was not increased in patients with stenosis/occlusion and normal autoregulation ( 1.5%, adjusted OR 0.6, 95% CI 0.2-1.6). Conclusions: Cerebrovascular reserve capacity evaluated by preoperative transcranial Doppler carbon dioxide testing is a major determinant of stroke risk in patients with carotid artery stenosis/occlusion undergoing cardiac surgery with cardiopulmonary bypass. Its assessment facilitates identification of patients with an excess perioperative stroke risk.