BIVA and VExUS for hydration assessment and cardiovascular mortality prediction in cardiorenal patients

Objectives. Despite advances in pharmacological treatment, heart failure (HF) remains a leading cause of hospitalization, mortality, and healthcare costs. HF often coexists with chronic kidney disease (CKD), impacting diagnosis, prognosis, and treatment. This study aims to evaluate correlations between bioelectrical impedance vector analysis (BIVA), ultrasound via VExUS, biomarkers (Ca125), and clinical outcomes assessing congestion and predicting cardiovascular mortality in patients with cardiorenal syndrome (CRS).Approach. This prospective observational study included 85 patients with HF and CKD assessed at the Endocardiorenal Unit of Virgen de la Victoria University Hospital. Patients underwent a comprehensive evaluation including BIVA (AKERN BIA 101 BIVA® device), ultrasound assessment (General Electric Vivid T8 system device) for VexUS evaluation, and biomarkers (Ca125, NT-proBNP). BIVA measurements were taken using a 50 kHz phase-sensitive impedance analyzer to measure resistance (R) and reactance (Xc). Statistical analysis involved Pearson's correlation and Cox regression to determine the relationships between these methods and mortality risk.Main results. Among the 85 patients (mean age 75.2 ± 8.4 years, 58.8% men), 11 cardiovascular and 8 non-cardiovascular deaths occurred over a 12-month follow-up. Strong statistically significant association was found between age, low hemoglobin levels, NYHA dyspnea, and mortality. Moderate statistically significant association was observed between BIVA hydration (HYDRAGRAM® calculated by device) and VExUS (r= 0.51,p< 0.001), with a hydration cut-off point of 78.7% predicting cardiovascular mortality. There was also a significant association between reactance (p= 0.03) and phase angle (PhA) (p= 0.006) with mortality. Cox regression analysis showed that patients with higher hydration had 5.43 times the risk of mortality compared to those with lower hydration (HR = 5.43, 95% CI: 1.36-21.61,p= 0.016).Significance. Integrating BIVA, VExUS, and Ca125 effectively assesses congestion in CRS patients. A BIVA-derived hydration threshold >78.7% was independently associated with 12-month cardiovascular mortality, supporting its value for risk stratification and improving patient management.