Abstract

Background: Heart failure with reduced ejection fraction (HFrEF) poses a significant global health burden with high mortality rates. Hyponatremia is a common electrolyte disorder with prognostic significance but remains underappreciated in clinical practice in Vietnam. This study aimed to describe the clinical and subclinical characteristics and determine the short-term prognostic value of serum sodium concentration in patients with HFrEF.

Methods: A cross-sectional descriptive study with longitudinal follow-up was conducted on 44 patients diagnosed with HFrEF admitted to the Department of Cardiology, Vietnam - Cuba Dong Hoi Friendship Hospital from March 2024 to December 2024. Clinical and laboratory parameters, especially serum sodium concentration at admission, were collected. SPSS 26.0 software was used to analyze correlations and prognostic value via ROC curves.

Results: The mean age was 77.52 ± 9.4 years. The prevalence of hyponatremia (<135 mmol/L) was 45.5%. Serum sodium concentration was strongly negatively correlated with NT-proBNP levels (r = -0.733; p < 0.001), moderately correlated with NYHA class (r = -0.472; p = 0.001), and fairly strongly correlated with length of hospital stay (r = -0.633; p < 0.001). The hyponatremia group had worse treatment outcomes than the normonatremia group (p = 0.003). Serum sodium level showed good prognostic value for treatment response (AUC = 0.854), with a cut-off of 129.9 mmol/L providing 82.9% sensitivity and 77.8% specificity.

Conclusions: Hyponatremia is a common finding, closely related to the severity of heart failure, and serves as a valuable short-term prognostic marker for treatment outcomes in patients with HFrEF.