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

BackgroundAlthough 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.MethodsA 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).ResultsHyponatremia (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.ConclusionEarly recovery from hyponatremia in AHF patients is associated with lower in-hospital mortality rate.