The ratio of furosemide dosage to urinary sodium concentration predicts mortality in patients with chronic stable heart failure

INTRODUCTION: The urinary sodium (UNa) concentration is associated with outcomes in patients with acute heart failure (HF). Its impact in individuals with chronic HF is unknown. OBJECTIVES: This study examined the combined effect of diuretic dosage and UNa concentration in chronic HF. PATIENTS AND METHODS: The research sample for this retrospective cohort study consisted of ambulatory patients receiving optimized therapy and followed in an HF clinic. The patients were recruited between 2009 and 2012. The exclusion criteria were therapeutic adjustments or hospital admissions in the previous 2 months and renalreplacement therapy. The patients were followed for 5 years; the endpoint was all‑cause mortality. The association between the ratio of furosemide dosage to UNa concentration and 5‑year mortality was studied using a receiver operating characteristic (ROC) curve. The patients were cross‑classified according to daily furosemide dosage (with the cutoff set at 80 mg) and UNa concentration (80 mEq/l). Multivariable Cox regression analysis was used to assess the prognostic impact of the ratio. RESULTS: We analyzed 283 patients with chronic HF (70.3% male; mean age, 69 years). During follow‑up, 134 patients died. The median furosemide dosage was 80 mg/day and the mean UNa concentration was 85 mEq/l. Based on the ROC curve, the best cutoff for the ratio of daily furosemide dosage to UNa concentration was 0.8. Patients with a ratio of 0.8 or higher had an adjusted hazard ratio for 5‑year mortality of 2.85 (95% CI, 1.78-4.58). Patients with a UNa excretion rate of less than 80 mEq/l who wereadministered 80 mg or more of furosemide per day were found to have a worse prognosis (HR, 4.15; 95% CI, 2.31-7.45) when compared with those with a UNa excretion rate of 80 mEq/l or more and less than 80 mg furosemide per day. CONCLUSIONS: Combining the diuretic dosage and measurement of UNa excretion can be used to refine risk stratification in chronic HF. The furosemide‑to‑UNa ratio can be a surrogate marker for diuretic resistance and has a prognostic impact in chronic HF.