Cognitive outcomes after on- versus off-pump coronary artery bypass surgery

Background: The Randomized On versus Off Bypass trial found no difference for a global cognitive outcome measure for patients receiving on-pump versus off-pump coronary artery bypass graft surgery (CABG). In this report, we present the baseline patient characteristics that were predictive of post-CABG cognitive decline as well as compare cognitive outcomes between treatment arms.

Methods: A neuropsychological battery was administered preoperatively and at 1 year after undergoing CABG. Stepwise regression was used to identify demographic or clinical risk factors associated with cognitive decline. Neuropsychological data were converted to demographically corrected T scores to provide impairment levels.

Results: Overall 1,156 patients (581 on-pump, 575 off-pump) completed match-paired neuropsychological assessments at baseline and 1-year follow-up. Baseline cognitive score, age, education level, and ethnicity predicted cognitive decline after CABG. Only 20% of either group had mild impairment at baseline on three of the test scores, and less than 10% had severe impairment on individual tests at either time. Few subjects in either group transitioned to clinically impaired levels at follow-up on individual tests.

Conclusions: At baseline, lower cognitive function, older age, lower education, and ethnicity other than white were predictive of cognitive decline after CABG. Patients in both groups demonstrated low frequencies of cognitive impairment on individual tests at baseline and follow- up, and few patients in either group were classified as impaired at 1-year follow-up on individual tests. In general, the Randomized On versus Off Bypass study documented that neither on-pump nor off-pump CABG adversely impacts long-term brain function.