The impact of hyponatremia on clinical outcomes and prognosis in patients with acute decompensated heart failure

Introduction

Hyponatremia is a common electrolyte disorder in heart failure (HF) and a strong predictor of mortality. Its pathophysiology is complex, and its prognostic value, particularly in acute decompensated heart failure (ADHF), remains unclear. This study aims to evaluate the prevalence of hyponatremia in ADHF, compare clinical profiles, and assess its prognostic impact on in-hospital and long-term outcomes.

Methods

we conducted a prospective observational study including 446 consecutive patients hospitalized with ADHF between 2020 and 2026. Patientswere classified according to serum sodium levels at admission into hyponatremic (Na <135 mEq/L) and normonatremic groups. Clinical, demographic, pharmacological, laboratory and echocardiographic variables were systematically analyzed (table 1). Survival analysis was conducted using the Kaplan-Meier method. Median follow-up was 9 months [4-18].

Results

Hyponatremia was present in 46 patients (10.3%). Baseline demographic characteristics and comorbidities, including hypertension, were similar between groups, with a high comorbidity burden reflected by the Charlson index.

Patients with hyponatremia showed a more advanced heart failure profile, characterized by lower cardiac output (20% vs. 8%, p=0.03) and a trend toward greater biventricular dysfunction. Despite similar renal function, hyponatremic patients exhibited an increased diuretic resistance and significantly higher NT-proBNP levels at admission (8478 vs. 4408 pg/mL, p=0.04), which remained persistently elevated at discharge and during follow-up. This pattern suggests a profile of greater volume overload and a worse clinical evolution.

Hyponatremia was associated with higher in-hospital mortality (6.5% vs. 1.3%, p=0.01), higher mortality during follow-up (34% vs. 16%, p<0.01), and a higher rate of cardiovascular death (24% vs. 11%, p=0.02). Kaplan–Meier analysis (figure 2) demonstrated significantly increased all-cause mortality (log-rank p=0.03) and heart failure readmission (log-rank p=0.01) in patients with hyponatremia, while cardiovascular mortality showed a non-significant trend (log-rank p=0.08).

Conclusion(s)

1)Hyponatremia affects 10% of patients with ADHF and identifies a subgroup with more advanced heart failure despite similar baseline comorbidities and renal function. 2) It is associated with a hemodynamic profile characterized by lower cardiac output, biventricular dysfunction, and greater congestion. 3) Hyponatremic patients show higher and persistently elevated NT-proBNP levels and greater diuretic requirements, suggesting more severe volume overload. 4)Hyponatremia is a strong marker of poor prognosis, being associated with increased in-hospital and long-term mortality as well as higher rates of heart failure readmission.Table 1.Baseline characteristicsFor image description, please refer to the figure legend and surrounding text.Figure 2.Kaplan Meier analysisFor image description, please refer to the figure legend and surrounding text.