Outcome measures - The primary outcome measures are evidence of new ischemic lesions on 48-hour DWI or 30-day DWI or FLAIR, or clinical evidence of new stroke if protocol required scans are not performed, determined at 30 days after surgery. The proportion of patients in each group with primary outcome variable will be tested by a chi-square for proportions. Secondary imaging outcome variables will include the number of new lesions, and the total volume of new ischemic lesions. Secondary outcome measure include all cause mortality, encephalopathy, 30-day and 6-month cognitive decline, evidence of reperfusion injury on 48-hour post-gadolinium FLAIR, new ischemic lesions on 6-month DWI or FLAIR, and changes in values of blood markers. The relationships among new ischemic lesions, cognitive decline, and changes in blood markers will be explored. The association of baseline variables to the prediction of new lesions will be explored using multivariate logistic regression procedures.