Background: Cognitive decline is well recognized early after coronary artery bypass graft surgery (CABG), but controversy exists regarding the degree and duration of these changes. We investigated the course of cognitive performance during 3 years after surgery and determined whether ischemic brain injury detected by diffusion-weighted magnetic resonance imaging was related to cognitive decline.
Methods: Thirty-nine patients undergoing on-pump CABG completed preoperative neuropsychologic examination and were followed up prospectively at discharge, 3 months, and 3 years after surgery. Cognitive performance was assessed with a battery of 11 standardized psychometric tests assessing 7 cognitive domains. Cognitive outcome was analyzed by determining (1) mean changes in within-patient scores over time (identifying cognitive functions with decline), and (2) the incidence of cognitive deficit for each individual (identifying patients with decline). Objective evidence of acute cerebral ischemia was obtained by diffusion-weighted magnetic resonance imaging. Prospectively collected data were used to identify predictors of cognitive deficits.
Results: From baseline to discharge, cognitive test scores significantly declined in 7 measures. Most tests improved by 3 months. Between 3 months and 3 years, late decline was observed in 2 measures with persistent deterioration in 1 measure (verbal memory) relative to baseline. Postoperative cognitive deficits (drop of > or = 1 SD in scores on > or = 3 tests) were observed in 56% of patients at discharge, 23% at 3 months and 31% at 3 years. On postoperative diffusion-weighted magnetic resonance imaging, there were new ischemic cerebral lesions in 51% of patients. The presence of cognitive deficit at discharge was a significant univariate predictor of late cognitive decline (p = 0.025). A relation between the presence of new diffusion-weighted magnetic resonance imaging detected lesions and cognitive decline, however, was not found.
Conclusions: Longitudinal cognitive performance of patients with CABG showed a two-stage course with early improvement followed by later decline. Long-term cognitive deficit was predicted by early cognitive decline, but not by ischemic brain lesions on magnetic resonance imaging.