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

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.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/Llog-rank test).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.