Admission hypochloremia and early chloride trajectories as markers of difficult decongestion in acute heart failure

Background Hypochloremia is common in acute heart failure, but it remains uncertain whether early in-hospital chloride trajectories provide clinically relevant information beyond chloride status at admission. Among patients with paired admission and 48–72-hour chloride measurements, we evaluated the association of admission hypochloremia with decongestion-related outcomes and examined whether early chloride trajectories provided additional information. Methods This retrospective cohort included 301 adults hospitalized with acute heart failure. Admission hypochloremia was defined as serum chloride < 98 mmol/L and was compared with admission normochloremia (≥ 98 mmol/L). Separate multivariable logistic regression models examined physician-documented diuretic resistance and residual congestion at discharge as the principal decongestion outcomes; worsening renal function and 90-day heart failure readmission were evaluated as secondary outcomes. The readmission analysis was restricted to patients discharged alive. Four chloride-trajectory categories were subsequently evaluated as exploratory exposures, and model fit was compared using the Akaike information criterion and likelihood-ratio tests. Results Admission hypochloremia was present in 102 patients (33.9%). After adjustment for age, sex, body mass index, heart failure phenotype, admission estimated glomerular filtration rate, albumin, log-transformed N-terminal pro-B-type natriuretic peptide, and right ventricular dysfunction, admission hypochloremia was associated with the principal decongestion outcomes of physician-documented diuretic resistance (adjusted odds ratio [OR], 2.68; 95% confidence interval [CI], 1.51–4.77; p < 0.001) and residual congestion (adjusted OR, 2.79; 95% CI, 1.52–5.13; p = 0.001). A less robust secondary association was observed with worsening renal function (adjusted OR, 1.86; 95% CI, 1.01–3.42; p = 0.046). The analysis did not demonstrate a clear association between admission hypochloremia and 90-day heart failure readmission among 292 patients discharged alive (adjusted OR, 1.37; 95% CI, 0.68–2.76; p = 0.385). Four-category trajectory models did not demonstrate statistically significant incremental fit over admission-status models for any outcome. Conclusions Among patients who underwent paired chloride measurement, admission hypochloremia was associated with physician-documented diuretic resistance and residual congestion. The association with worsening renal function was a less robust secondary finding. Early chloride trajectories did not significantly improve model fit beyond admission chloride status.