Endothelial Activation and Stress Index Predicts Mortality in Critically Ill Atrial Fibrillation Patients: A Retrospective Cohort Analysis Using the MIMIC-IV Database

Background The Endothelial Activation and Stress Index (EASIX) reflects endothelial dysfunction and has prognostic value in cardiovascular diseases. This study investigates the association between EASIX and all-cause mortality in critically ill atrial fibrillation (AF) patients. Methods Using MIMIC-IV (v3.1) data, 4722 AF patients were stratified by EASIX quartiles. Cox regression, Kaplan-Meier curves, and restricted cubic spline (RCS) models assessed mortality risk at 7, 30, 180, and 365 days. Subgroup analyses evaluated consistency. Results EASIX was significantly associated with increased mortality at all time points. The Kaplan-Meier survival curve shows that as the EASIX quartile increases, the 7-day, 30-day, 180-day, and 365-day mortality rates of AF patients significantly increase. RCS analyses showed that there was a significant non-linear relationship between EASIX and the 7-day, 30-day, 180-day, and 365-day mortality rates of patients with AF. The Cox analysis before and after adjusting for confounding factors showed that EASIX was an independent risk factor for 7-day, 30-day, 180-day, and 365-day all-cause mortality in AF patients. Subgroup analyses further indicated the robustness of these results. Conclusions EASIX levels are significantly correlated with all-cause mortality at 7, 30, 180, and 365 days in patients with AF, and endothelial dysfunction plays an important role in poor prognosis in AF patients.