The impact of prediuretic urine osmolarity and urine osmolarity change on long-term outcomes in acute heart failure patients during early decongestion

Background The osmolarity seems to be an essential indicator of balance between water and osmotically active molecules. This balance is critical in acute heart failure (AHF), especially in light of the quality of diuretic response and urine dilution. However, despite developing advances in decongestion assessment methods, the outcome in this clinical condition remains unfavorable. Therefore, we assessed the significance of serum and urine osmolarity for long-term outcome prediction in AHF. Purpose The study aimed to determine serum osmolarity and pre- and post-diuretic urine osmolarity association with long-term outcomes in patients hospitalized due to AHF. Methods That was a prospective study conducted at our institute involving patients hospitalized for AHF who required diuretic treatment. Serum and urine osmolarity, were assessed before diuretic administration and 3 hours after diuretic infusion began. Outcomes, defined as: 1.) all cause mortality, 2.) unplanned rehospitalizations were tracked over a one-year follow-up. Results The study included 236 patients, 69% male, with a mean age of 65±14 years. Most patients had HF with reduced ejection fraction (56%), mean LVEF of 38±15%, and 34% revealed AHF de novo. The NT-proBNP was 6872 [3746–12301] pg/mL. During the one-year follow-up, 58 patients (24%) died, and 89 (37%) experienced urgent rehospitalizations. Pre-diuretic urine osmolarity was significantly lower in patients with poor outcomes compared to those with favorable outcomes (361 [272–406] vs. 425 [342–519] mOsm/L, p<0.001 for mortality; 384 [310–465] vs. 435 [349–538] mOsm/L, p=0.001 for rehospitalization) (Fig 1 A). Moreover, the patients experienced unfavorable events were characterized by lower urine osmolarity drop (-24 [-70 - -8] vs -127 [-214 - -53] mOsm/L; p<0.001 for all-cause death, and -68 [-155 - -11] and -128 [-216 - -55] mOsm/L; p=0.003 for rehospitalizations) (Fig 1 B). In contrast, serum osmolarity and post-diuretic urine osmolarity showed no significant differences between groups. The univariate and multivariate analysis (adjustment for known prognostic factors) showed that the higher the pre-diuretic osmolarity, the lower the odds for unfavorable event occurrence (Fig 2 A). Moreover, the change of urine osmolarity (difference between post-diuretic and pre-diuretic one) was a predictive factor of poor outcome (the lower the drop, the worse the outcome) (Fig 2 B). Serum osmolarity and post-diuretic urine osmolarity lacked prognostic significance for poor outcomes in AHF. Conclusion Urine osmolarity prior to diuretic administration and change of the urine osmolarity during decongestive treatment are associated with long-term outcomes in AHF. The significance of high pre-diuretic urine osmolarity is linked to better outcomes, reflecting the greater potential for diuretic response ("dilute the urine") in AHF.