Improvement in hyponatremia during hospitalization for worsening heart failure is associated with improved outcomes: Insights from the Acute and Chronic Therapeutic Impact of a Vasopressin Antagonist in Chronic Heart Failure (ACTIV in CHF) trial

Background: Hyponatremia predicts poor outcome in patients with acute heart failure syndromes. This study evaluated the relationship between baseline serum sodium, change in serum sodium, and 60-day mortality in hospitalized heart failure patients. Methods: A post-hoc analysis of the ACTIV in CHF trial was performed. ACTIV in CHF randomized 319 patients hospitalized for worsening heart failure to placebo or one of three tolvaptan doses. Cox proportional hazards regression-analysis was used to explore the relationship between baseline hyponatremia, sodium change during the hospitalization, and 60-day mortality. Results: Hyponatremia was observed in 69 patients (21.6%). After covariate adjustment, baseline hyponatremia was a statistically significant predictor of 60-day mortality (P=0.0016). Follow-up serum sodium data were available in 68 patients. At hospital discharge, 45 of 68 (66.2%) hyponatremic patients had improvements in serum sodium levels (≥2 mmol/l). Hyponatremic patients with a serum sodium improvement had a mortality rate of 11.1% at 60 days post discharge, compared with a 21.7% mortality rate in those showing no improvement. After covariate adjustment, change in serum sodium was a statistically significant predictor of 60-day mortality (HR: 0.736, 95% CI: 0.569-0.952 for each 1-mmol/l increase in serum sodium from baseline). Conclusions: Serum sodium improvements during hospitalization for heart failure were associated with improved survival at 60 days.