Impact of low cardiac function and diabetes mellitus on survival and causes of death following coronary artery surgery

OBJECTIVES: To determine the differential impact of low cardiac function (ejection fraction [EF] ≤ 35%) and diabetes mellitus (DM) on survival and to identify causes of death after coronary artery bypass grafting (CABG). METHODS: Overall, 1036 patients who underwent isolated CABG between 2009 and 2022 were divided into four groups based on EF and DM. Kaplan-Meier analysis was performed to calculate each group's estimated survival. Inter-group multivariate Cox regression was performed with the reference group showing EF > 35% and DM (-). Additional Cox regressions were performed to investigate the associations of EF ≤ 35% and DM (+) with death from heart failure, myocardial infarction, cancer, pneumonia, cerebrovascular disease and renal failure. RESULTS: Off-pump techniques were used in 980 patients (95%). Patient population and estimated 10-year postoperative survival were as follows: EF > 35% DM (-), 430, 75.1%; EF > 35% DM (+), 456, 66.3%; EF ≤ 35% DM (-), 73, 62.5%; and EF ≤ 35% DM (+), 77, 53.5%. Hazard ratios (HRs) (P values) for the three groups were as follows: EF > 35% DM (+), 1.53 (0.006); EF ≤ 35% DM (-), 1.84 (0.017); and EF ≤ 35% DM (+), 2.23 (0.001). For death from heart failure, HR (P value) for EF ≤ 35% versus EF > 35% was 3.62 (0.012). For deaths from cancer and pneumonia, HRs (P values) for DM (+) versus DM (-) were 1.73 (0.097), and 2.72 (0.046), respectively. CONCLUSIONS: EF ≤ 35% and DM (+) are associated with worse post-CABG survival. Each is associated with specific causes of death.