Associations of Bioelectrical Impedance-Derived Phase Angle and Hydration Parameters with Clinical Severity in Ambulatory Chronic Heart Failure

Background/Objectives: Malnutrition and altered body composition are frequent in chronic heart failure (HF) and are associated with worse functional status and prognosis. Bioelectrical impedance analysis (BIA) is increasingly used in nutritional assessment, although its interpretation may be confounded by fluid overload. This study aimed to evaluate the association between BIA-derived parameters and clinical and biochemical markers of disease severity in ambulatory patients with chronic heart failure. Methods: This cross-sectional study included adult outpatients with chronic HF consecutively assessed in a specialised HF unit. Nutritional evaluation comprised anthropometry, handgrip strength, rectus femoris muscle ultrasound and BIA. Phase angle (PA) and hydration-related parameters were analysed in relation to New York Heart Association (NYHA) functional class and N-terminal pro-B-type natriuretic peptide (NT-proBNP) levels. Multivariable regression models adjusted for relevant clinical and BIA variables were applied. Results: A total of 115 patients were included (mean age 68.2 ± 12.6 years; 71.3% men). Mean PA was 4.6 ± 1.1°. Lower PA was independently associated with greater dyspnoea severity (p = 0.026) and higher NT-proBNP concentrations (p = 0.014). Higher total body water was positively associated with symptom burden (p = 0.013) and NT-proBNP levels (p < 0.001) and showed good discriminatory performance for identifying patients in the highest NT-proBNP quartile. Conclusions: In ambulatory patients with chronic HF, BIA-derived parameters reflecting cellular integrity and hydration status are independently associated with clinical and biochemical markers of disease severity. BIA may provide complementary information in nutritional assessment, although hydration-related confounding should be carefully considered. Future longitudinal studies should determine whether these bioimpedance-derived parameters can improve risk stratification and nutritional assessment in chronic heart failure.