Objective: This study aims to investigate the prognostic value of body mass index (BMI) in patients hospitalized with heart failure with mildly reduced ejection fraction (HFmrEF). 

Background: Limited data regarding the prognostic impact of BMI 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 patients with a BMI > 25 kg/m² was compared to patients with a BMI ≤ 25 kg/m². 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 patients with HFmrEF were included. Median BMI mean was 26.9 kg/m². Patients with BMI > 25 kg/m² presented with significantly lower aminoterminal pro-brain natriuretic peptide (NT-pro BNP) levels (median 5061 pg/ml vs. 11020 pg/ml; p=0.001). NT-pro BNP levels inversely correlated with BMI levels in HFmrEF patients. Notably, patients with BMI > 25 kg/m² were not associated with an increased risk of heart-failure related re-hospitalization (8% vs. 11%; log rank p=0.109; HR= 0.669; 95% CI 0.408 – 1.097; p=0.111). Even after multivariable adjustment, the risk of heart failure related re-hospitalization was not affected by BMI (HR= 0.768; 95% CI 0.464 – 1.271; p=0.305). Finally, the rates of in-hospital mortality (2.4% vs. 4.5%; p=0.131) and cardiovascular failure related re-hospitalization (18% vs. 19%; log rank p=0.703; HR=0.934; 95% CI 0.655 – 1.330; p=0.704) did not differ among patients with higher or lower BMI.

Conclusions: An obesity paradox was found revealing lower natriuretic peptide levels and no prognostic impact in HFmrEF patients.