Diffusion- and Perfusion-Weighted Magnetic Resonance Imaging of the Brain Before and After Coronary Artery Bypass Grafting Surgery

Abstract

Background and Purpose— Coronary artery bypass grafting (CABG) is a frequently performed surgical procedure that can be associated with neurological complications. Some studies have demonstrated that new focal brain lesions, detected by MRI, can develop after CABG. Furthermore, it has been suggested that the presence of such new lesions is associated with a decline in neurocognitive test scores. Advanced MRI techniques, including diffusion- (DWI) and perfusion-weighted imaging (PWI), offer important diagnostic advantages over conventional imaging in the assessment of patients undergoing CABG. We sought to determine whether focal PWI and DWI abnormalities could occur after CABG, particularly in patients without any measurable neurological deterioration. Methods— Thirteen patients prospectively underwent MRI with DWI and PWI before and after CABG. A battery of neurocognitive tests was administered before and after surgery. Demographic, clinical, and radiographic characteristics of the patients were collected and compared. Results— Four patients developed new DWI defects after CABG. The lesions were small, rounded, and multiple (3 of 4 patients). One of these patients was diagnosed with stroke on clinical grounds. The patients with new lesions had a larger neurocognitive decline than their counterparts with stable MRI. Other clinical characteristics of patients with new DWI lesions, including stroke risk factors, were similar to those of patients without MRI changes. No focal perfusion abnormalities were observed on preoperative or postoperative scans. Conclusions— Postoperative DWI abnormalities can occur after CABG, even in patients without overt neurological defects. The PWI scans remained unchanged. Larger prospective studies are required to determine whether the new lesions are clearly associated with neurocognitive decline or with specific perioperative stroke risk factors.