Key result
Low urinary sodium-to-furosemide index is linked to ~4-fold higher 30-day major events in worsening HF.
Why the study?
Spot urinary sodium is used to assess diuretic response in worsening heart failure but does not account for chronic loop diuretic exposure, limiting risk stratification.
Does the urinary sodium-to-furosemide index (NaU/F) improve short-term risk stratification compared with isolated urinary sodium in adults with ambulatory worsening heart failure?
Cohort (n=130)
No
Does the urinary sodium-to-furosemide index (NaU/F) improve short-term risk stratification compared with isolated urinary sodium in adults with ambulatory worsening heart failure?
Odds Ratio: 4.69 (95% CI 1.38–15.9)
Absolute Event Rate: 20% vs 5%
p-value: p=0.008
The NaU/F index, which adjusts urinary sodium for baseline loop diuretic dose, outperforms isolated urinary sodium for predicting 30-day adverse outcomes in ambulatory worsening heart failure.
NaU/F may refine short-term risk stratification versus NaU alone in ambulatory WHF; leaves open prospective validation before any practice change.
BACKGROUND: Worsening heart failure (WHF) carries high short-term morbidity and mortality. Spot urinary sodium (NaU) is increasingly used to assess diuretic response but does not account for chronic loop diuretic exposure. OBJECTIVES: To determine whether a urinary sodium-to-furosemide index (NaU/F) improves short-term risk stratification compared with isolated NaU in ambulatory WHF METHODS: Retrospective analysis of a prospective cohort of consecutive adults treated in a specialized heart failure day-hospital program (August 2023-April 2025). Spot NaU was measured 2 hours after intravenous loop diuretic administration. NaU/F was calculated as urinary sodium divided by baseline oral furosemide dose (40-mg equivalents). PRIMARY ENDPOINT: 30-day composite of HF rehospitalization, unplanned outpatient visit, or all-cause mortality. RESULTS: 130 patients were included (mean age 77.8 ± 10.8 years; 74.6% male; LVEF 42.2 ± 18.2%). The primary endpoint occurred in 10.9%. NaU <70 mmol/L showed modest prognostic performance (OR 2.70, 95% CI 0.85-8.57; p=0.08; AUC 0.67). NaU/F <26 mmol/40 mg was associated with higher event rates (20% vs 5%; OR 4.69, 95% CI 1.38-15.90; p=0.008) and better discrimination (AUC 0.77, 95% CI 0.67-0.86), remaining independently associated with the endpoint (p=0.02). CONCLUSION: In ambulatory WHF, NaU/F outperformed isolated urinary sodium for short-term risk stratification. Contextualizing natriuretic response to chronic loop diuretic exposure may refine prognostic assessment and warrants prospective validation.
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Burgos et al. (2026) conducted a cohort in Ambulatory worsening heart failure (n=130). Urinary sodium-to-furosemide index (NaU/F) <26 mmol/40 mg vs. NaU/F ≥26 mmol/40 mg was evaluated on 30-day composite of HF rehospitalization, unplanned outpatient visit, or all-cause mortality (OR 4.69, 95% CI 1.38-15.90, p=0.008). In ambulatory worsening heart failure, a urinary sodium-to-furosemide index <26 mmol/40 mg was associated with higher 30-day event rates (20% vs 5%; OR 4.69; 95% CI 1.38-15.90; p=0.008).
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