An unexpected inverse relationship between HbA1c levels and mortality in patients with diabetes and advanced systolic heart failure

Abstract

Background In diabetes, poor glycemic control, as indexed by hemoglobin A1c (HbA1c), is associated with increased risk of cardiovascular events and new-onset heart failure (HF). However, in patients with diabetes and HF, the relationship between glucose control and survival has not been investigated. Our study aimed to evaluate the relationship between HbA1c levels and mortality in patients with diabetes and advanced systolic HF.Methods We studied a cohort of 123 patients with diabetes and advanced systolic HF referred to a single center with HbA1c values measured at presentation. The patients were grouped based on HbA1c: HbA1c < or = 7.0 (n = 49) and HbA1c > 7.0 (n = 74).Results The cohort was 70% men, ejection fraction of 25% +/- 7, 59% ischemic etiology, HbA1c 7.9 +/- 1.8, and diabetes duration of 8.6 +/- 9.0 years. The HbA1c groups were similar in age; sex; New York Heart Association class; body mass index; diabetes duration; and insulin, metformin, and glitazone use. HbA1c > 7.0 was associated with higher ejection fraction, increased beta-blocker, and sulfonlyurea use. Patients with HbA1c < or = 7.0 had significantly increased all-cause mortality, compared with those with HbA1c > 7.0 (35% vs 20%, hazard ratio 2.6, 95% CI 1.3-5.2, P < .01). In multivariate analysis, HbA1c < or = 7.0 remained associated with increased mortality (hazard ratio 2.3, 95% CI 1.0-5.2).Conclusions Paradoxically, elevated HbA1c levels were associated with improved survival in this cohort of patients with diabetes and advanced HF. Further investigation is necessary to determine the nature of this relationship and optimal HbA1c in patients with diabetes and HF.