Improvement of hyponatremia is associated with lower mortality risk in patients with acute decompensated heart failure: a meta-analysis of cohort studies.

Hyponatremia at admission is predictive of poor prognosis in patients with acute decompensated heart failure (ADHF). We performed a meta-analysis of cohort studies to evaluate whether improvement of hyponatremia is associated with improved survival in patients with ADHF and hyponatremia. Relevant studies were identified through systematic search of PubMed and Embase. A random-effect model was used to pool the results. Predefined subgroup analyses were performed to explore the source of heterogeneity. Five thousand seven hundred fourteen patients with ADHF and hyponatremia from eight cohort studies were included. Results showed that improvement of hyponatremia during hospitalization was associated with lower risk of all-cause mortality (RR = 0.65, 95% CI 0.53 to 0.80, p < 0.001) as compared with those without improvement of hyponatremia. Results of subgroup analyses indicated that improvement of hyponatremia was associated with more remarkable changes of short-term (within 3 months after discharge) mortality (RR = 0.54) as compared with long-term mortality (RR = 0.74). Other factors such as study design, sample size, and heart failure subtypes did not affect the association. This was further confirmed by the meta-analysis of studies with multivariate analysis, which also suggested an association between improved hyponatremia and lower risk of all-cause mortality in ADHF patients (adjusted RR = 0.63, 95% CI 0.43 to 0.92, p = 0.02; I = 63%). These results suggested that improvement of hyponatremia in ADHF patients is associated with lower mortality risk during follow-up, particularly for the short-term mortality.