Low Serum Sodium as a Poor Prognostic Indicator for Mortality in Congestive Heart Failure Patients

Background: The incidence of congestive heart failure (CHF) has not significantly declined over the past 50 years, and overall survival rates are low at 5 years following diagnosis. Numerous studies have shown low serum sodium to be a poor prognostic indicator of all cause mortality in CHF patients. Hypothesis: The goal of this hypothesis was to validate if hyponatremia is an important predictor of mortality in an outpatient population of CHF patients on maximal combined angiotensin-converting enzyme inhibitor (ACEI) and beta-blocker therapy. Methods: A total of 364 (13% with hyponatremia) patients with CHF (ejection fraction [EF] <= 40%) were enrolled in a heart failure disease management program. The mean New York Heart Association (NYHA) class was II.XII. The average baseline serum sodium was 138.2 mEq/L. Results: We evaluated the relationship between hyponatremia (<135 mEq/L) and all-cause mortality at 40 months. During follow-up, 8 patients in the hyponatremia group compared to 31 in the normonatremic group died. Results of Kaplan-Meier analyses indicated there were no significant differences in mortality between the hyponatremia and normonatremic groups (log-rank test = 0.39). Results for Cox proportional hazards models indicated low sodium was not a significant predictor of mortality (unadjusted odds ratio [OR]: 1.41, 95% confidence interval [CI]: 0.65, 3.07; adjusted OR: 1.60, 95% CI: 0.57, 4.53). Conclusions: The relationship between hyponatremia and all-cause mortality did not reach significance. Hyponatremia did not significantly predict mortality in a CHF population on maximal medical therapy.