The relationship between serum creatinine-to-albumin ratio (CAR) and prognosis in critically ill patients with acute heart failure admitted to the ICU: A retrospective study based on the MIMIC-IV database

Acute heart failure (AHF) remains associated with high short- and long-term mortality, particularly in patients admitted to the intensive care unit (ICU). Reliable biomarkers for early risk stratification are urgently needed. The creatinine-to-albumin ratio (CAR), integrating renal function and nutritional–inflammatory status, may serve as a novel prognostic marker in critically ill AHF patients. We conducted a retrospective cohort analysis using the Medical Information Mart for Intensive Care IV database, including 7620 patients with a 1st ICU admission for AHF. CAR was calculated from serum creatinine and albumin measured at ICU admission. The primary endpoint was 28-day all-cause mortality; secondary endpoints included 180-day and 365-day all-cause mortality. Survival outcomes were analyzed using Kaplan–Meier curves, Cox proportional hazards regression models, and restricted cubic spline analyses. Patients with higher CAR levels had significantly higher 28-, 180-, and 365-day mortality (all log-rank P < .001). In multivariate Cox models, elevated CAR was independently associated with increased mortality, and this association was consistent across all adjustment models. Restricted cubic spline analyses confirmed a nonlinear dose–response relationship between CAR and short- and long-term mortality risk. Subgroup analyses demonstrated consistent associations across most patient subgroups, without significant interactions. CAR is a simple and accessible prognostic biomarker that independently predicts short- and long-term mortality in critically ill patients with AHF admitted to the ICU. Incorporating CAR into clinical practice may improve early risk stratification and guide management decisions. Prospective studies are warranted to validate its clinical utility.