Long-term mortality is increased in patients with undetected prediabetes and type-2 diabetes hospitalized for worsening heart failure and reduced ejection fraction.

Background We assessed the prevalence of newly diagnosed prediabetes and type-2 diabetes mellitus (T2DM), and their impact on long-term mortality in patients hospitalized for worsening heart failure with reduced ejection fraction (HFrEF). Methods We included patients hospitalized with HFrEF and New York Heart Association (NYHA) functional class II-III. Baseline two-hour oral glucose tolerance test was used to classify patients as normoglycaemic or having newly diagnosed prediabetes or T2DM. Outcomes included post-discharge all-cause and cardiovascular mortality during the median follow-up of 2.1 years. Results At baseline, out of 150 patients (mean-age 57 +/- 12 years; 88% male), prediabetes was diagnosed in 65 (43%) patients, and T2DM in 29 (19%) patients. These patients were older and more often with NYHA class III symptoms, but distribution of comorbidities was similar to normoglycaemic patients. Taking normoglycaemic patients as a reference, adjusted risk of all-cause mortality was significantly increased both in patients with prediabetes (hazard ratio, 2.6; 95% confidence interval (CI), 1.1-6.3; p = 0.040) and in patients with T2DM (hazard ratio, 5.3; 95% CI, 1.7-15.3; p = 0.023). Likewise, both prediabetes (hazard ratio, 2.9; 95% CI, 1.1-7.9; p = 0.041) and T2DM (hazard ratio, 9.7; 95% CI 2.9-36.7; p = 0.018) independently increased the risk of cardiovascular mortality compared with normoglycaemic individuals. There was no interaction between either prediabetes or T2DM and heart failure aetiology or gender on study outcomes (all interaction p-values > 0.05). Conclusions Newly diagnosed prediabetes and T2DM are highly prevalent in patients hospitalized for worsening HFrEF and NYHA functional class II-III. Importantly, they impose independently increased long-term risk of higher all-cause and cardiovascular mortality.