Glycemic Control in Type 1 Diabetes and Long-Term Risk of Cardiovascular Events or Death After Coronary Artery Bypass Grafting

BackgroundPatients with type 1 diabetes mellitus (T1DM) have a high risk of cardiovascular events.ObjectivesThe aim of this study was to investigate whether preoperative hemoglobin A1c (HbA1c) levels could predict cardiovascular events or death after coronary artery bypass grafting (CABG).MethodsThis was a nationwide population-based observational cohort study that included all patients with T1DM who underwent primary isolated nonemergency CABG in Sweden between 1997 and 2012, according to the Swedish National Diabetes Register and the SWEDEHEART (Swedish Web-system for Enhancement and Development of Evidence-based care in Heart disease Evaluated According to Recommended Therapies) register. We calculated the crude incidence rates and 95% confidence intervals (CIs) and used Cox regression and multivariable hazard ratios (HRs) to estimate the risk of both all-cause mortality and major adverse cardiovascular events (MACE), defined as myocardial infarction, stroke, heart failure, or repeat revascularization, in relation to HbA1c levels.ResultsIn total, 764 patients with T1DM were included. During a median follow-up of 4.7 years, 334 (44%) patients died or had MACE (incidence rate: 82 events/1,000 person-years). After multivariable adjustment, the HR (95% CI) for death or MACE in patients with HbA1c levels of 7.1% to 8.0%, 8.1% to 9.0%, 9.1% to 10.0%, and >10.0% were 1.34 (0.82 to 2.21), 1.59 (1.00 to 2.54), 1.73 (1.03 to 2.90), and 2.25 (1.29 to 3.94), respectively, compared with the reference category. When HbA1c was used as a continuous variable, the HR for a 1% increase in HbA1c level was 1.18, and the 95% CI was 1.06 to 1.32.ConclusionsIn patients with T1DM, poor glycemic control before CABG was associated with increased long-term risk of death or MACE. (HeAlth-data Register sTudies of Risk and Outcomes in Cardiac Surgery [HARTROCS]; NCT02276950)