Prognosis of diabetic patients undergoing coronary artery bypass surgery compared with nondiabetics: a systematic review and meta-analysis.

OBJECTIVE: The influence of diabetes mellitus (DM) on mortality and morbidity in patients undergoing coronary artery bypass graft (CABG) surgery has remained uncertain due to conflicting conclusions from clinical trials measuring the association between diabetes and perioperative risk. Therefore, a quantitative meta-analysis was undertaken to evaluate the available evidence from prospective and historic cohort clinical trials. The purpose of this study was to determine the significance and magnitude of impact of DM on mortality, morbidity and resource-related outcomes for patients undergoing CABG over the past few decades and in the contemporary setting.
METHODS: MEDILINE, EMBase, BIOSIS Preview, CBMDisc, CNKI and WanFang databases were searched, supplemented by hand search, without language limitations, for studies published from January 1981 to October 2008. Data extraction included study design, setting, inclusion/exclusion criteria, population characteristics, statistical method, length of follow-up and clinical outcomes. Eligible studies were assessed for quality.
RESULTS: Of the 132 identified studies, 24 cohort studies with a median follow-up of 4.3 years were selected for analysis. A total of 100,217 patients (28,168 with DM and 72,049 without DM), were included in the meta-analysis. The pooled RR (95% CI) for mortality of diabetic versus non-diabetic patients was significantly increased at 30 days (RR 1.64, 95% CI 1.39, 1.93), 1 year (RR 1.83, 95% CI 1.56, 2.15), 3 years (RR 1.81, 95% CI 1.58, 2.09), 5 years (RR 1.66, 95% CI 1.53, 1.79) and 10 years (RR 1.55, 95% CI 1.43, 1.68) after CABG. Significant differences were also found for DM versus non-DM patients post-CABG for perioperative cerebrovascular accidents (RR 1.52; 95% CI 1.31, 1.77), postoperative acute renal failure (RR 1.63; 95% CI 1.48, 1.79), sternal infection (RR; 1.70, 95% CI 1.41-2.04) and blood transfusion (RR 1.15; 95% CI 1.08, 1.21). No significant differences were found for postoperative atrial fibrillation (AF), postoperative myocardial infarction (MI) and re-exploration for bleeding. Insufficient and/or heterogeneous data did not allow for pooled analysis of ventilator time, ICU stay, angina recurrence, repeat revascularization, hospital stay and hospital costs.
CONCLUSIONS: Current evidence suggests that patients with DM who are undergoing CABG are at increased risk of mortality, stroke, renal failure, sternal infection and blood transfusion when compared to those without DM. This increased relative risk for perioperative mortality and complications has remained, despite evolving definitions of DM and practice patterns. Future randomized studies should focus on interventions targeted toward these complications to mitigate the risk for patients with DM.