Impact of type 2 diabetes mellitus on the long-term mortality in patients who were treated by coronary artery bypass surgery A systematic review and meta-analysis

Background: Recent scientific reports have mainly focused on the comparison between coronary artery bypass surgery (CABG) and percutaneous coronary intervention. However, the impact of type 2 diabetes mellitus (T2DM) on mortality in patients who were treated by CABG was often ignored. Therefore, we aimed to compare the long-term mortality following CABG in patients with and without T2DM. Methods: Studies comparing the long-term adverse outcomes following CABG in patients with and without T2DM were searched from electronic databases. Total number of deaths (primary outcome) and events of myocardial infarction (MI), major adverse cerebrovascular and cardiovascular events (MACCEs), stroke, and repeated revascularization (secondary outcomes) were carefully extracted. An analysis was carried out whereby odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using the RevMan 5.3 software. Results: Eleven studies with a total number of 12,965 patients were included. Current results showed that mortality was significantly higher in patients with T2DM with OR: 1.54, 95% CI: 1.37 to 1.72, P<.00001; OR: 1.53, 95% CI: 1.36 to 1.72, P<.00001; and OR: 1.53, 95% CI: 1.26 to 1.87, P<.0001 at 1 to 15, 5 to 15, and 7 to 15 years, respectively. However, MI, repeated revascularization, MACCEs, and stroke were not significantly different with OR: 1.15, 95% CI: 0.81 to 1.64, P=.44; OR: 1.09, 95% CI: 0.88 to 1.36, P=.43; OR: 1.11, 95% CI: 0.83 to 1.48, P=.48; and OR: 1.69, 95% CI: 0.93 to 3.07, P=.08, respectively. Conclusion: Following CABG, a significantly higher rate of mortality was continually observed in patients with T2DM compared to patients without T2DM showing that the former apparently has a high impact on the long-term mortality. However, even if T2DM is an independent risk factor for mortality, it should not be ignored that CABG remains the best revascularization strategy in these patients.