Low-Normal Serum Sodium and Heart Failure-Related Events in Patients With Heart Failure With Preserved Left Ventricular Ejection Fraction

BACKGROUND: Hyponatremia has been shown to be a prognostic factor in heart failure (HF) with preserved ejection fraction (HFpEF). Serum sodium (sNa) cut-off, however, is not defined in HFpEF. Therefore, we investigated the relationship between sNa and HF-related events (cardiovascular death and hospitalization for HF decompensation) in HFpEF patients. METHODS AND RESULTS: We assessed cardiac function using echocardiography and measured sNa in HFpEF patients with New York Heart Association class II (n=321) or III (n=84) in a compensated condition after implementing medical therapy for HF. During a mean follow-up of 27 months, 73 patients developed HF-related events. On multivariate Cox hazard analysis including established predictors in HF, sNa level as a continuous variable was identified as an independent predictor for HF-related events in HFpEF (per 1.0 mmol/L: HR, 0.93; 95% CI: 0.87-0.98; P<0.01). Kaplan-Meier analysis demonstrated significantly higher probability of HF-related events in the lower sNa group (sNa <140 mmol/L) than in the higher sNa group (sNa ≥140 mmol/L; P<0.001, log-rank test). Further, the low-normal sNa group (135 mmol/L<sNa<140 mmol/L) was significantly associated with HF-related events compared with the higher sNa group (P<0.001, log-rank test). CONCLUSIONS: sNa as a continuous variable was independently correlated with future HF-related events in HFpEF. Low-normal sNa could provide important prognostic information for practical risk stratification in HFpEF.