Role of spot urinary sodium in outpatients with heart failure

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.