BRAIN MAGNETIC-RESONANCE-IMAGING IN CORONARY-ARTERY BYPASS GRAFTS - APREOPERATIVE AND POSTOPERATIVE ASSESSMENT

We undertook a study to determine (1) the frequency and prognostic sig nificance of preexisting MRI brain abnormalities in patients undergoin g coronary artery bypass grafts (CABG) and (2) whether MRI can detect surgery-related brain damage in 31 neurologically asymptomatic CABG pa tients (mean age, 61.0 +/- 6.6 years). MRIs were performed within 7 da ys before and 8 to 17 days after surgery. When we compared the preoper ative images with those of 31 age- and risk factor-matched neurologica lly asymptomatic controls free of cardiac disease (mean age, 60.3 +/- 6.1 years), higher rates of thromboembolic infarcts (16% versus 0%), l acunes (58.1% versus 32.3%), and brainstem lesions (22.6% versus 3.8%) were noted. Subjective rating demonstrated significantly larger ventr icles in patients than in controls (p = 0.002). CABG candidates also h ad significantly increased ventricular-to-intracranial cavity ratios ( VICR) as determined by semiquantitative volumetric measurements (6.9 /- 2.5% versus 4.9 +/- 1.6%; p = 0.0004). Eleven patients had postsurg ical complications, with eight having symptoms consistent with diffuse encephalopathy. The only MRI finding that separated encephalopathic f rom complication-free patients was ventricular size (VICR 9.0 +/- 2.5% versus 4.9 +/- 1.6%; p = 0.006). This difference remained statistical ly significant after adjustment for the effects of age (p = 0.04). Pos toperative MRI consistently failed to demonstrate surgery-related brai n damage responsible for the encephalopathy.