Residual congestion and urinary sodium and chloride trajectories in acute heart failure.

Residual congestion remains frequent after initial treatment for acute heart failure (AHF), and its presence may not be adequately identified using individual clinical or biochemical markers. We investigated residual congestion using a multimodal approach and examined its relationship with changes in urinary sodium and chloride during the first 72 h of hospitalization. We prospectively included consecutive patients hospitalized for AHF who underwent congestion assessment at admission and 72 h. Clinical evaluation, NT-proBNP, and venous Doppler ultrasound (VExUS) were integrated to assess congestion. Residual multimodal congestion was defined by the presence of at least two of three criteria: VExUS score ≥ 1, < 30% reduction in NT-proBNP, and clinical congestion score ≥ 3. Urinary sodium and chloride were measured at admission and 72 h, and their changes over time were evaluated using linear mixed-effects models. Baseline estimated glomerular filtration rate (eGFR), worsening renal function, and urinary albumin-to-creatinine ratio were additionally characterized. Among 146 patients, 67 (45.9%) had residual multimodal congestion at 72 h. Urinary sodium and chloride concentrations were lower in patients with residual congestion. Both electrolytes decreased during the first 72 h (p < 0.001 for both), but their changes differed according to residual congestion status, with significant time-by-group interactions for sodium (p = 0.013) and chloride (p = 0.001). Patients with residual congestion also showed a trend toward poorer 180-day event-free survival, although this difference did not reach statistical significance (log-rank p = 0.078). Patients with residual congestion showed different early patterns of urinary sodium and chloride during treatment for AHF. Serial measurement of these electrolytes may complement clinical, biochemical, and venous ultrasound assessment when evaluating the response to decongestive therapy. These findings support their potential role in characterizing different decongestive profiles, although their clinical and prognostic value requires further evaluation.