Association of longitudinal blood urea nitrogen trajectory with in-hospital and 28-day mortality in acute heart failure with cardiorenal syndrome

BACKGROUND AND OBJECTIVE: Patients with acute heart failure (AHF) complicated by acute cardiorenal syndrome (CRS) demonstrate substantial mortality risk. Conventional blood urea nitrogen (BUN) assessments using single-point measurements inadequately capture the temporal dynamics of renal dysfunction and disease progression. This study investigated the prognostic utility of BUN trajectory patterns for predicting in-hospital and 28-day mortality in AHF patients with CRS. METHODS: We conducted a retrospective cohort study using the Medical Information Mart for Intensive Care IV (MIMIC-IV) database as the derivation cohort and the eICU Collaborative Research Database (eICU-CRD) as the validation cohort. BUN measurements were obtained at baseline ( 0.05 for non-linearity), though with inconsistent predictive performance. Compared with the persistent-high trajectory group, the persistent-low trajectory group demonstrated significantly reduced in-hospital mortality (derivation cohort: OR 0.47, 95% CI 0.27-0.85; validation cohort: OR 0.59, 95% CI 0.38-0.93) and 28-day mortality (derivation cohort: HR 0.56, 95% CI 0.34-0.94; validation cohort: HR 0.66, 95% CI 0.45-0.85). Subgroup analyses indicated enhanced predictive performance of the persistent-low trajectory group in non-diabetic patients across both cohorts. No significant interactions were observed across subgroups, including different acute kidney injury stages. CONCLUSION: BUN trajectory patterns provide independent prognostic information for short-term outcomes in AHF patients with CRS. Persistent-low BUN trajectory are associated with significantly improved survival compared to persistent-high trajectory.