Diuretic resistance in acute heart failure: proposal for a new urinary sodium-based definition

Background: Diuretic resistance is a relevant clinical issue in acute heart failure (AHF), but a standardized, quantitative definition is still missing. The aim of this analysis was to highlight discrepancies between previously proposed definitions of diuretic response and to propose a new urinary sodium (NaU)-based definition of diuretic efficiency (DE) to identify diuretic resistant (DR) patients. Methods: Three historical definitions of diuretic response and a new NaU-based DE definition, evaluating total NaU after the first diuretic bolus per 40 mg furosemide administered, were applied in a retrospective analysis to an AHF population treated with intravenous (i.v.) loop diuretics. Baseline characteristics, in-hospital clinical data and outcomes at discharge and mid-term follow-up were collected and compared among DR and non-DR patients for each definition. Results: Among 53 patients, 39 (73.6%), 51 (96.2%) and 3 (5.7%) were DR according to weight-derived, diuresisderived, and spot NaU definition, respectively. The median value of the new NaU-based definition was 31 mmol/ 40 mg and patients were stratified accordingly. DR patients showed lower cumulative diuresis (5200 mL, 3300-6700 vs 9825 mL, 6200-12200, p = 0.007) and weight loss (4 kg, 1-5 vs 6 kg, 3-8.5, p = 0.023), higher BNP levels (808 pg/mL, 443-1037 vs 351 pg/mL, 209-859, p = 0.062) at the conclusion of protocol-guided i.v diuretic therapy, which was less frequently stopped due to decongestion in DR as compared to non-DR patients (57.7% vs 85.2%, p = 0.026). Six-months mortality or HF hospitalizations were more frequent in DR patients (OR 18.6, 95% CI 2.1-161.2, p = 0.008). Conclusions: The NaU-based DE definition might solve discrepancies of other previously proposed definitions.