Mid-Term Outcomes After Coronary Artery Bypass Grafting and the Impact of Glucose Metabolism Disorders on Prognosis

Objective: To assess the relationship between preoperative glycemic status (normoglycemia, prediabetes, and overt type 2 diabetes mellitus) and mid-term (4-year) outcomes after coronary artery bypass grafting (CABG). Methods: The analysis included 693 patients who underwent elective CABG between 1 May 2016 and 1 May 2018 and had known glycemic status. The median follow-up among survivors was 50 months (4.2 years; range 29–73 months). Based on preoperative glycemic status, actively diagnosed using an oral glucose tolerance test, patients were divided into three groups: normoglycemia (n = 293), prediabetes (n = 229), and type 2 diabetes mellitus (T2DM, n = 171). Major adverse cardiovascular events (MACE) were defined as death from any cause, myocardial infarction, or stroke. Kaplan–Meier analysis, logistic regression, and Cox proportional hazards regression were used to assess predictors of adverse outcomes. Results: A clear gradient in adverse event rates emerged across the three glycemic categories: lowest in normoglycemia, intermediate in prediabetes, and highest in T2DM. All-cause mortality was 10.6% in normoglycemia, 15.3% in prediabetes, and 28.7% in T2DM (p < 0.001 for Groups 1–3; p = 0.001 for Groups 2–3). MACE occurred in 15.7%, 24.5%, and 39.2%, respectively (p < 0.001). Prediabetes was associated with a higher incidence of MACE than normoglycemia (24.5% vs. 15.7%; p = 0.002) but not with higher mortality. Kaplan–Meier analysis showed significantly lower survival in patients with any glucose metabolism disorder (p = 0.002) and in those with T2DM (p < 0.001) compared with normoglycemia; freedom from MACE was significantly higher in normoglycemia than in T2DM (p < 0.001), prediabetes (p = 0.007), and any glucose metabolism disorder (p < 0.001). In multivariable logistic regression, T2DM was independently associated with MACE after adjustment for sex, age, combined procedures, and eGFR (OR 1.59, 95% CI 1.33–1.90; p < 0.001); prediabetes remained independently associated after adjustment for sex, age, combined procedures, CPB duration, and eGFR (OR 1.21, 95% CI 1.05–1.40; p = 0.009); any glucose metabolism disorder was associated with MACE after adjustment for sex, age, combined procedures, and eGFR (OR 1.31, 95% CI 1.16–1.48; p < 0.001). In Cox proportional hazards regression, independent predictors of mid-term mortality and MACE were decreased renal function (p = 0.046 and p = 0.037, respectively), aortic cross-clamp time (p < 0.001 for both), and the presence of any glucose metabolism disorder (p < 0.001 for both). Conclusions: Preoperative glucose metabolism disorders were associated with worse mid-term (4-year) outcomes after CABG. T2DM was associated with higher all-cause mortality, whereas prediabetes was associated with a higher incidence of MACE but not with mortality. These observational findings support the clinical relevance of identifying and managing prediabetes before CABG, although causal effects cannot be inferred.