Cognitive outcome after coronary artery bypass surgery: a longitudinal assessment with a three year follow-up

Objectives: Cognitive decline is commonly reported after coronary artery bypass grafting (CABG). In the few studies that follow-up patients beyond the immediate postoperative period, there is controversy regarding the degree and duration of cognitive changes. We assessed the course of cognitive function during 3 years after CABG and determined the relation between cognitive decline and structural brain injury detected by magnetic resonance imaging.

Methods: In patients undergoing CABG (n=39), neuropsychological tests and MRI were performed preoperatively, at discharge, 3 months and 3 years after surgery. Cognitive performance was assessed with a series of tests (n=13), measuring various cognitive areas. Cognitive decline was defined as a drop of 1 SD or more in the scores in 3 or more tests.

Results: Cognitive decline was present in 72% (28/39) of patients at discharge, 28% (11/39) at 3 months and 31% (11/32) at 3 years. Of the 28 patients with cognitive decline at discharge, 20 (71%) patients improved to baseline performance at 3 months. Of the 11 patients with decline at 3 years, only 3 showed deficits during the entire postoperative period, while 8 revealed early improvement followed by later decline. Postoperative MRI disclosed new small brain lesions in 51% of patients. All lesions were neurologically silent. Cognitive decline was not related to brain lesions, clinical or operative variables (regression analysis).

Conclusion: Cognitive decline early after CABG frequently resolves within few months, and late deficits may often not be related to the operation. A predictor of postoperative cognitive decline was not identified.