In diabetes, poor glycemic control, as indexed by hemoglobin A1_c (HbA_1c), 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 HbA_1c levels and mortality in patients with diabetes and advanced systolic HF.

We studied a cohort of 123 patients with diabetes and advanced systolic HF referred to a single center with HbA_1c values measured at presentation. The patients were grouped based on HbA_1c: HbA_1c ≤7.0 (n = 49) and HbA_1c >7.0 (n = 74).

The cohort was 70% men, ejection fraction of 25% ± 7, 59% ischemic etiology, HbA_1c 7.9 ± 1.8, and diabetes duration of 8.6 ± 9.0 years. The HbA_1c groups were similar in age; sex; New York Heart Association class; body mass index; diabetes duration; and insulin, metformin, and glitazone use. HbA_1c >7.0 was associated with higher ejection fraction, increased β-blocker, and sulfonlyurea use. Patients with HbA_1c ≤7.0 had significantly increased all-cause mortality, compared with those with HbA_1c >7.0 (35% vs 20%, hazard ratio 2.6, 95% CI 1.3-5.2, P < .01). In multivariate analysis, HbA_1c ≤7.0 remained associated with increased mortality (hazard ratio 2.3, 95% CI 1.0-5.2).

Paradoxically, elevated HbA_1c 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 HbA_1c in patients with diabetes and HF.