Relation between serum sodium levels and clinical outcomes in Turkish patients hospitalized for heart failure: a multi-center retrospective observational study

Objective: The purpose of the study was to analyze the prevalence of hyponatremia and related 1-year outcomes of patients hospitalized for decompensated heart failure with reduced ejection fraction (HFrEF) in Turkish patients. Methods: A total of 500 hospitalized patients with HFrEF were consecutively included in a retrospective study at 19 participating hospitals. Patients were categorized according to their serum sodium levels (sNa) on admission day as normonatremic (135–145 mEq/L) and hyponatremic (<135 mEq/L). One-year all-cause mortality, re-hospitalization rates, and the impact of the changes in sNa at the time of discharge to clinical outcomes were examined. Results: Hyponatremia was observed in 29% of patients. Patients with hyponatremia had lower blood pressures, creatinine clearance, and left ventricular ejection fraction and higher serum creatinine and BUN levels on admission compared with those with normonatremia. Hyponatremia was associated with higher 1-year all-cause mortality (14% vs. 2.6%, p<0.001) and re-hospitalization rates (46.9% vs. 33.7%, p=0.005). After adjustment for covariates, hyponatremia was independently associated with 1-year all-cause mortality (adjusted HR, 4.762; 95% CI, 1.941–11.764; p=0.001). At discharge, only 50.8% of hyponatremic patients were corrected to normonatremia (≥135 mEq/L). Those with persistent hyponatremia had the highest all-cause mortality (p<0.001). Conclusion: In this study, it is demonstrated that hyponatremia is relatively common and is associated with increased 1-year all-cause mortality and re-hospitalization rates among Turkish patients hospitalized with HFrEF. Approximately 50% of the patients with initial low sNa had persistent hyponatremia at discharge, and these patients had the worst clinical outcomes.