Objective: This study aims to investigate the prognostic value of type 2 diabetes mellitus (diabetics) in patients hospitalized due to heart failure with mildly reduced ejection fraction (HFmrEF).  

Background: Limited data regarding the prognostic impact of diabetes mellitus in patients with HFmrEF is available.

 Methods: A large retrospective registry was used including all consecutive hospitalized patients with HFmrEF (i.e., left ventricular ejection fraction (LVEF) 41 – 49%) from 2016 to 2022 according to current European guidelines. The prognostic impact of diabetics was compared to non-diabetics. The primary endpoint was the first heart-failure related re-hospitalization at 3 years. Secondary endpoints comprised amongst others in-hospital mortality. Kaplan-Meier, uni- and multivariable Cox regression analyses were applied for statistics.
Results: 803 consecutive HFmrEF patients were included (33% diabetics with a median glycated hemoglobin (HbA1c) of 7.5%; 67% non-diabetics with a median HbA1c of 5.5%). Aminoterminal pro-brain natriuretic peptide (NT-pro BNP) levels on admission were comparable between diabetics and non-diabetics (6770 pg/ml vs. 5335 pg/ml; p= 0.369) on admission. Diabetics were associated with an increased risk of heart-failure related re-hospitalization (12% vs. 7%; p=0.046; HR=1.607; 95% CI 1.005 – 2.568; p=0.048) at 3 years. After multivariable adjustment, the risk of heart failure related re-hospitalization was still significantly higher in diabetics (HR=1.916; 95% CI 1.001 – 3.667; p=0.049). In contrast, no significant difference was observed regarding in-hospital mortality (4% vs. 3%; p=0.462). 
Conclusions: Diabetics with HFmrEF revealed higher rates of heart failure related re-hospitalization compared to non-diabetic HFmrEF patients.