Recovery from hyponatremia in acute phase is associated with better in-hospital mortality rate in acute heart failure syndrome

Background: Although hyponatremia on admission is a predictor of poor prognosis in acute heart failure (AHF) patients, little is known about the association between changes in sodium level in acute phase and in-hospital mortality. This study was performed to clarify the impact of sodium level improvement in the early phase on prognosis in AHF patients.

Methods: A total of 882 consecutive hospitalized AHF patients were retrospectively enrolled in this study. Sodium levels were evaluated on days 1 and 3 of admission, and patients were classified into three groups: patients with hyponatremia on admission and day 3 (hypo-hypo group); patients with hyponatremia on admission and normonatremia on day 3 (hypo-normo group); and patients with normonatremia on admission (normo group).

Results: Hyponatremia (sodium ≤135 mEq/L) was observed in 14.3% of cases. In multivariate linear regression analysis, age (standardized beta=0.084), male gender (standardized beta=-0.072), history of ischemic heart disease (standardized beta=-0.069), baseline sodium level (standardized beta=-0.435), and tolvaptan use (standardized beta=0.093) were independent determinants of changes in sodium level from day 1 to day 3. In-hospital mortality rates were significantly higher in the hypo-hypo group (23.7%) and hypo-normo group (9.7%) than the normo group (6.9%) (p<0.001). After adjustment for covariates, both hypo-normo (OR: 0.28, 95% CI: 0.08-0.93, p=0.038) and normo (OR: 0.42, 95% CI: 0.20-0.88, p=0.022) groups showed significantly lower in-hospital mortality rates than the hypo-hypo group.

Conclusion: Early recovery from hyponatremia in AHF patients is associated with lower in-hospital mortality rate.