Brain magnetic resonance imaging abnormalities following off-pump cardiac surgery

Neurological and cognitive deficits are known complications after coronary artery bypass surgery (CABG) and are believed to be secondary to brain ischemia. Diffusion-weighted magnetic resonance imaging (DW-MRI) of the brain is especially sensitive and can depict ischemic areas that may not be evident clinically or with conventional MRI. Abnormalities found at brain MRI following CABG performed with cardiopulmonary bypass (ie, on pump) have been reported, but data are limited for CABG performed without use of cardiopulmonary bypass (ie, off pump). The objective of this study was to determine the rate of DW-MRI detection of brain lesions following off-pump CABG.

Sixteen patients consecutively undergoing off-pump CABG underwent DW-MRI prior to and after surgery. A neuroradiologist blinded to patient data coded the location and size of lesions. Neurological function was assessed with the National Institutes of Health Stroke Scale. Five (31%) of the patients had new focal ischemic lesions found at postoperative DW-MRI. Risk factors for postoperative brain ischemic lesions were similar between patients with and those without lesions found at DW-MRI. No patient had a definite clinical stroke after surgery.

Ischemic lesions found at DW-MRI are seen after off-pump CABG at a rate similar to that reported for CABG with cardiopulmonary bypass. This finding suggests that these lesions are not totally due to cardiopulmonary bypass. Further prospective clinical studies would be helpful for determining which factors are causally related to brain ischemia following CABG.