Assessing intrinsic renal sodium avidity in acute heart failure: implications in predicting and guiding decongestion

Intrinsic renal sodium avidity (IRSA) is a hallmark feature of acute heart failure (AHF) and can be measured by evaluating the urinary sodium (UNa) concentration. The aim of this study is to assess the role of measuring IRSA through a random Una-sample and its association with decongestive response.

A post-hoc analysis of the ROSE-AHF trial was performed in all patients with a random UNa spot sample before randomization (n = 339/360). Patients were categorized according to tertiles of UNa as high (range 19-40 mmol/L), intermediate (range 41-68 mmol/L), or low (range 69-139 mmol/L) IRSA. Linear mixed effect models and ANCOVA were used to assess the relation with decongestive effectiveness measured by: (i) weight change, (ii) visual analogue scale (VAS) improvement, (iii) N-terminal pro-B-type natriuretic peptide (NT-proBNP) change, (iv) natriuretic response (UNa in mmol/L), (v) 72 h natriuresis (mmol), (vi) oedema resolution, and (vii) length of stay. High IRSA patients had less improvement in decongestive metrics, including weight loss (p = 0.028), VAS improvement, NT-proBNP decrease, natriuretic response (p-time interaction <0.001 for all), had lower total natriuresis (high IRSA 438 ± 141 mmol, intermediate IRSA 526 ± 320 mmol, and low IRSA 603 ± 276 mmol; p < 0.001), exhibited more oedema at 72 h (p = 0.005), and had a longer length of stay (p = 0.015). Incremental loop diuretic dose titration (± 4 times home dose) after >24 h, resulted in an increase in natriuretic response in the high IRSA group, however cumulative natriuresis still remained lower at 72 h (p < 0.001). Longitudinal UNa profiling of patients with low IRSA showed physiologic breaking in the UNa pattern, associated with attaining decongestion and slight increase in creatinine and cystatin C, forming a potential signal of complete decongestion.

A simple random UNa sample at the time of AHF, gives insight into IRSA which is consistently associated with decongestive effectiveness across multiple metrics, offering an opportunity for early AHF care improvement.