Does Preoperative Mild Cognitive Impairment Predict Postoperative Cognitive Dysfunction after On-Pump Coronary Bypass Surgery?

BACKGROUND: Mild cognitive impairment (MCI) may contribute to the development of postoperative cognitive dysfunction (POCD) after coronary artery bypass grafting (CABG). OBJECTIVE: The aim of this study was to investigate the incidence of early and long-term POCD after CABG in coronary heart disease patients with and without preoperative MCI. METHODS: The study enrolled two groups of males with coronary heart disease: 51 without MCI (mean age 56.0 ± 6.42 years) and 50 with MCI (mean age 56.4 ± 5.55 years). Baseline clinical characteristics as well as durations of cardiopulmonary bypass and aortic cross-clamping were similar between the two groups. MCI was defined as a Mini-Mental State Examination score of less than 28. All patients underwent detailed neuropsychological examinations (12 tests) before and 7-10 days and 1 year after surgery. The incidence of early and long-term POCD was estimated on the basis of criteria defined as a 20% decline on 20% of the tests. RESULTS: Early POCD was diagnosed in 72% of cases in patients with MCI and in 79% of those without MCI (p = 0.5; odds ratio [OR] = 0.68; 95% confidence interval [CI] 0.2-2.2). Long-term POCD was diagnosed in 72% of MCI patients and in 70% of non-MCI patients (p = 0.8); OR = 1.08 (95% CI 0.4-2.9). CONCLUSIONS: Our results show that the presence of MCI is not the leading cause of either early or long-term POCD in patients undergoing CABG. Further research should focus on the contribution of important clinical factors, including progression of atherosclerosis and adherence, to post-CABG POCD.