Prognostic value of hyponatremia in heart failure patients: an analysis of the Clinical Characteristics and Outcomes in the Relation with Serum Sodium Level in Asian Patients Hospitalized for Heart Failure (COAST) study

Abstract

Background/aims: Hyponatremia is a well-known risk factor for poor outcomes in Western studies of heart failure (HF) patients. We evaluated the predictive value of hyponatremia in hospitalized Asian HF patients.

Methods: The Clinical Characteristics and Outcomes in the Relation with Serum Sodium Level in Asian Patients Hospitalized for Heart Failure (the COAST) study enrolled hospitalized patients with systolic HF (ejection fraction < 45%) at eight centers in South Korea, Taiwan, and China. The relationship between admission sodium level and clinical outcomes was analyzed in 1,470 patients.

Results: The mean admission sodium level was 138 ± 4.7 mmol/L, and 247 patients (16.8%) had hyponatremia defined as Na(+) < 135 mmol/L. The 12-month mortality was higher in hyponatremic patients (27.9% vs. 14.6%, p < 0.001), and hyponatremia was an independent predictor of 12-month mortality (hazard ratio, 1.72; 95% confidence interval, 1.12 to 2.65). During hospital admission, 57% of hyponatremic patients showed improvement without improvement in their clinical outcomes (p = 0.620). The proportion of patients with optimal medical treatment was only 26.5% and 44.2% at admission and discharge, respectively, defined as the combined use of angiotensin-converting-enzyme inhibitor/angiotensin receptor blocker and β-blocker. Underuse of optimal medical treatment was more pronounced in hyponatremic patients.

Conclusions: In hospitalized Asian HF patients, hyponatremia at admission is common and is an independent predictor of poor clinical outcome. Furthermore, hyponatremic patients receive less optimal medical treatment than their counterparts.

Keywords: East Asians; Hospitalized heart failure; Hyponatremia; Predictor of clinical outcomes.

Figure 1. Clinical outcomes based on serum sodium levels. (A) Hospitalized hyponatremic patients had a higher 12-month mortality rate, (B) higher 12-month rehospitalization rate, and (C) higher composite 12-month mortality and rehospitalization rate. The distribution of patients with normonatremia (NN), improved hyponatremia (iHN), and persistent hyponatremia (pHN) was 78.4%, 12.3%, and 9.3%, respectively. The 12-month postdischarge mortality was lowest in the NN group (15.9%) compared to iHN (29.8%) and pHN groups (30.4%). (D) The outcome did not differ between iHN and pHN groups (p = 0.620), suggesting that short-term changes in HN status were not associated with improved clinical outcomes.