Relation Between Hemoglobin A1c and Outcomes in Heart Failure Patients With and Without Diabetes Mellitus

In patients with diabetes mellitus (DM) in the general population, elevated glycosylated hemoglobin (HbA1c) increases the risk for developing heart failure (HF). However, in patients with established HF, the association of HbA1c level with outcomes is not well established. The aim of this study was to investigate the relation between HbA1c and outcomes in patients with HF with and without DM. A total of 845 patients with advanced HF followed at the Ahmanson-UCLA Cardiomyopathy Center were studied, stratified by the presence (n = 358) or absence (n = 487) of DM and by DM-specific HbA1c quartiles (patients with DM: Q1 ≤6.4%, Q2 6.5% to 7.2%, Q3 7.3% to 8.5%, and Q4 ≥8.6%; patients without DM: Q1 ≤5.6%, Q2 5.7% to 6.0%, Q3 6.1% to 6.5%, and Q4 ≥6.6%). The primary outcomes analyzed were death and death or urgent heart transplantation. In the cohort with DM, 2-year event-free survival was 61% and 65% in Q3 and Q4 compared to 48% and 42% in Q1 and Q2 (p = 0.005). In the cohort without DM, there was no difference in outcomes by HbA1c quartile. Risk-adjusted analysis in the diabetic cohort showed significantly increased hazard ratios for death or urgent heart transplantation in Q1 and Q2 compared to Q4. For every unit HbA1c increase, there was a 15% decreased hazard ratio of death or urgent heart transplantation and all-cause mortality (p = 0.006 and p = 0.036, respectively). In the cohort without DM, multivariate models revealed similar hazard ratios among HbA1c quartiles. In conclusion, in this cohort of patients with advanced HF, higher HbA1c levels were associated with improved outcomes in patients with DM. This relation was not observed in patients without DM. Further investigations into mechanisms underlying the relation between HbA1c, DM, and survival in advanced HF are warranted.