Risk analysis of the association between EASIX and all-cause mortality in critical ill patients with atrial fibrillation: a retrospective study from MIMIC-IV database

The Endothelial Activation and Stress Index (EASIX) is a recognized marker of vascular endothelial health but has limited application in patients with atrial fibrillation (AF). This study aimed to explore the association between EASIX and prognosis in critically ill patients with AF. The patient's data were extracted from Medical Information Mart for Intensive Care IV(MIMIC-IV) database. EASIX was calculated as lactate dehydrogenase (U/L) × creatinine (mg/dL)/platelets (109 cells/L) and log2-transformed for statistical analysis. The Boruta algorithm and Least Absolute Shrinkage and Selection Operator (Lasso) Regression were used for feature selection. Multivariable logistic regression and Cox proportional hazard models were employed to assess EASIX as a risk factor, with nonlinear relationships evaluated using restricted cubic spline curves. The area under the receiver operating characteristic curve (AUC) was utilized to compare the predictive performance of EASIX with the Sequential Organ Failure Assessment (SOFA) score and the CHA₂DS₂-VASc score. Furthermore, Kaplan-Meier survival analysis based on EASIX quartiles (with Q1 as the reference) and stratified analyses were conducted to further explore these associations. A total of 4896 patients with complete data were included. In-hospital, 28-day, and 365-day all-cause mortality rates were26.04%, 29.25%, and 49.75%, respectively. The median EASIX was 5.64 (4.56, 6.84). Higher EASIX was significantly associated with increased in-hospital, short-term, and long-term all-cause mortality after multivariable adjustment. Patients in quartiles Q2, Q3, and Q4 had significantly higher mortality than those in Q1, showing a clear trend. Kaplan-Meier analysis confirmed that patients with higher EASIX scores had significantly lower survival. The AUC showed that the performance of EASIX in predicting both short-term and long-term all-cause mortality was comparable to the SOFA and higher than the CHA₂DS₂-VASc score. Stratified analyses indicated that the association remained robust across subgroups, accounting for various underlying conditions and hospital interventions. EASIX is a reliable predictor of both short- and long-term mortality in critically ill patients with AF. Future prospective studies are necessary to confirm its broader applicability in other populations.