Prognostic Significance of Serum Sodium in Patients With Acute Pulmonary Embolism

Abstract

Background: Hyponatremia has been associated with adverse outcomes in several cardiovascular diseases; however, its independent prognostic value in patients with acute pulmonary embolism (APE) remains uncertain.

Methods: We conducted a single-center retrospective observational study of 105 hospitalized patients with confirmed APE between January 2020 and June 2025. Baseline clinical characteristics were compared between 1-year survivors and non-survivors. Serum sodium levels at the time of APE diagnosis were assessed, and hyponatremia was defined as a serum sodium level < 135 mmol/L. Univariable and multivariable Cox proportional hazards regression analyses were performed to evaluate the association of serum sodium and other potential prognostic factors with 1-year mortality.

Results: Among 105 hospitalized patients with confirmed APE, 41 (39.0%) died within 1 year. Non-survivors had a higher prevalence of active cancer (61.0% vs. 15.6%, P < 0.001) and chronic obstructive pulmonary disease (COPD) (21.9% vs. 1.6%, P = 0.001), lower systolic blood pressure (108.9 ± 25.9 vs. 130.8 ± 21.6 mm Hg, P<0.001), and higher Pulmonary Embolism Severity Index (PESI) scores (157.3 ± 56.0 vs. 91.0 ± 32.7, P < 0.001) than survivors. Serum sodium at diagnosis was significantly lower in non-survivors than in survivors (130.6 ± 5.9 vs. 136.4 ± 4.4 mmol/L, P < 0.001), and hyponatremia was more frequent among non-survivors (78.1% vs. 35.9%, P < 0.001). In univariable Cox regression, hyponatremia was associated with increased 1-year mortality (univariable hazard ratio (uHR), 4.20; 95% confidence interval (CI), 2.00–8.81; P < 0.001). After adjustment for disease severity and relevant clinical risk factors, serum sodium at diagnosis remained independently associated with 1-year mortality (multivariable hazard ratio (mHR) per 1-mmol/L increase, 0.92; 95% CI, 0.86–0.99; P = 0.043).

Conclusions: Lower serum sodium at diagnosis was independently associated with increased 1-year mortality in hospitalized patients with APE. Hyponatremia may represent a simple and readily available prognostic marker for early risk stratification in APE. Larger prospective studies are needed to confirm these findings.