Introduction: Heart failure (HF) and atrial fibrillation (AF) and are two interrelated pathologies with common risk factors, both being associated with an extended length of hospital stay (LOS).

Objective: To identify factors that influence LOS in patients with HF and AF.

Methods: This study evaluated retrospectively patients with AF and HF admitted consecutively in a tertiary University Hospital from January 2018 to June 2019. We included patients with all types of documented AF (paroxysmal, persistent and permanent) and HF, regardless of the cause of hospital admission. Prolonged LOS was defined as more than 7 days (defined by the 75 percentile for all cohort).

Results: 620 patients with a mean age of 73 ± 10.04 years with HF and AF were included in this study. 53.39% were females. 48.26% patients had HF with preserved ejection fraction (HFpEF) and 50.16% permanent AF. The median duration of hospitalization was 4 days and 18.66% had prolonged LOS. Common comorbidities included ischemic heart disease (23.75%) hypertension (79.64%), diabetes mellitus (31.83%), anemia (70.04%), dyslipidemia (45.07%) and chronic kidney disease (37.32%). In univariate analysis, acute decompensated HF (RR 1.34, 95%CI 1.23-1.47, p< 0.001), dyspnea at rest (RR 1.92, 95% CI 1.13-3.26, p= 0.0003), HFrEF (RR 1.23, 95%CI 1.09-1.38, p= 0.0009), dementia (RR 1.54, 95%CI 1.02-2.32, p= 0.001), eGFR< 30ml/min/1.73m2 (RR 1.30, 95%CI 1.01-1.71, p= 0.0007) and anemia (RR 1.37, 95%CI 1.1491-1.6378, p= 0.001) were associated with prolonged LOS. Higher levels of NT-proBNP and creatinine were linked with the length of hospital stay with an AUC 0.711 (95% CI 0.658-0.763, p< 0.000), cut -off value of 10046 pg/dl, respectively AUC 0.573 (95%CI 0.515-0.630, p= 0.013), cut-off value of 1.7mg/ dl. In multiple regression analysis, after adjusting for age and sex, NT-proBNP (p< 0.001) and dyspnea at rest (p< 0.001) remained independent predictors of prolonged LOS.

Conclusions: In hospitalized patients with HF and AF, factors associated with prolonged LOS were ADHF, HFrEF, dementia, decreased renal function and anemia. The only independent predictors for prolonged LOS were NT-proBNP and dyspnea at rest.