Stroke during coronary bypass surgery: principal role of cerebral macroemboli

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Abstract
Objective: The purpose of this study was to gain insight into the etiology of stroke during coronary bypass surgery. Methods: Retrospective review of prospectively gathered data on 6682 consecutive coronary bypass patients. Patients undergoing simultaneous procedures, including carotid endarterectomy, were excluded. We performed a systematic chart review of all patients who suffered a perioperative stroke. Predictors of stroke were determined with stepwise logistic regression analysis. Results: The prevalence of stroke was 1.5% (n=98). Stroke patients had significantly increased intensive care unit and hospital length of stays, as well as increased mortality when compared to patients without stroke (all P≪ 0.001). Independent predictors of stroke were (in decreasing order of magnitude): age ≫70 years, left ventricular ejection fraction ≪40%, previous stroke or transient ischemic attack, normothermic cardiopulmonary bypass, diabetes, and peripheral vascular disease. Chart review revealed that the probable cause of stroke was macroemboli, likely from ascending aorta atherosclerosis, in 37% of patients and unknown in 38% of patients. Computerized tomography (CT) scans were obtained in 79 patients (81%). Lesions detected by CT were consistent with a macroembolic etiology: nearly all lesions were ischemic in nature and located in the distribution of major cerebral arteries, particularly the middle cerebral artery. Conclusions: Stroke is a devastating complication of coronary bypass surgery. Our multivariable risk factors for stroke, chart review, and CT findings all suggest that macroemboli, presumably from the ascending aorta, are the predominant cause of stroke during coronary bypass surgery. Future studies should be directed at minimizing the risk of embolization during cardiac surgery.