INTRODUCTION AND OBJECTIVES: Spot determination of urinary sodium (UNa+) has emerged as a useful tool for monitoring diuretic response in patients with acute heart failure (AHF). However, the evidence in outpatients is scarce. We aimed to examine the relationship between spot UNa+ levels and the risk of mortality and worsening heart failure (WHF) events in individuals with chronic HF. METHODS: This observational and ambispective study included 1145 outpatients with chronic HF followed in a single center specialized HF clinic. UNa+ assessment was carried out 1-5 days before each visit. The endpoints of the study were the association between UNa+ and risk of a) long-term death and b) AHF-hospitalization and total WHF events (including AHF-hospitalization, emergency department visits or parenteral loop-diuretic administration in HF clinic), assessed by multivariate Cox and negative binomial regressions. RESULTS: The mean±standard deviation of age was 73±11 years, 670 (58.5%) were men, 902 (78.8%) were on stable NYHA class II, and 595 (52%) had LFEF ≥50%. The median (interquartile range) UNa+ was 72 (51-94) mmol/L. Over a median follow-up of 2.63 (1.70-3.36) years, there were 293 (25.6%) deaths and 382 WHF events (244 AHF-admissions) in 233 (20.3%) patients. After multivariate adjustment, baseline UNa+ was inverse and linearly associated with the risk of total WHF (IRR, 1.07
95%CI, 1.02-1.12
P=.007) and AHF-admissions (IRR, 1.08
95%CI, 1.02-1.14
P=.012) and borderline associated with all-cause mortality (HR, 1.04
95%CI, 0.99-1.09
P=.068). CONCLUSIONS: In outpatients with chronic HF, lower UNa+ was associated with a higher risk of recurrent WHF events.