Body mass index in the context of acute heart failure and preserved left ventricular ejection fraction: a paradoxical effect of obesity?

Abstract Introduction Obesity is a common and multifactorial disease, classified according to Body Mass Index (BMI) categories. Although previous studies suggest that higher BMI might be associated with an increased risk of cardiovascular diseases, there is limited information available for patients with a diagnosis of acute heart failure (HF) and with a preserved left ventricular ejection fraction (HFpEF). Aims To assess baseline characteristics, comorbidities, clinical presentation and outcomes according to the BMI categories in patients with HFpEF and acutely admitted due to worsening HF. Methods In this single-centre, retrospective, observational study, data on patients with HFpEF and admitted due to acute HF from 1st January 2015 to 31st December 2019 were collected. Patients were classified into the currently accepted BMI categories: 18.5-24.9 kg/m2 (normal weight), 25-29.9 kg/m2 (overweight), 30-34.9 kg/m2 (class I obesity), 35-39.9 kg/m2 (class II obesity), ≥ 40 kg/m2 (class III obesity). Baseline characteristics, clinical presentation, blood tests and echocardiographic data were analysed according to the BMI categories. Independent predictors of BMI were identified using linear regression analysis and association between BMI and outcomes was assessed using Cox proportional hazard analysis. The composite of all-cause mortality or readmission due to AHF at 90 days after discharge was our primary outcome. Results Of the 3,073 patients enrolled (aged 81 years, of whom 47 % men), 1,346 (44%) reported normal weight, 1,090 (35%) overweight, whilst 439 (14%), 121 (4%) and 77 (3%) were in the I, II and III class of obesity, respectively. Patients with higher BMI were younger, had higher prevalence of hypertension, diabetes, atrial fibrillation, coronary artery disease and kidney failure. Compared to participants with normal weight, those with greater BMI presented decreased N-terminal pro brain natriuretic peptide (NT-proBNP) measurements, whereas echocardiographic variables did not significantly differ among the BMI categories. In the multivariate analysis, participants with a higher BMI had a lower incidence of the composite outcome of all-cause mortality or HF-related readmission compared to those with normal weight (p=0.001). Conclusions BMI is often elevated in patients diagnosed with HFpEF who are acutely hospitalized for worsening HF. Greater BMI values were associated with higher prevalence of hypertension, diabetes but lower NT-proBNP concentrations. Patients with increased BMI presented a lower risk of adverse outcomes, suggesting a potential and paradoxical protective effect of obesity on the prognosis of patients with HF.