Association between endothelial activation and stress index and mortality in critically ill patients with atrial fibrillation: In MIMIC database: A Retrospective Cohort Study

BACKGROUND: Evidence indicates that the Endothelial Activation and Stress Index (EASIX) is a predictor of mortality in endothelium-related conditions; however, its association with mortality risk in atrial fibrillation (AF) remains uncertain. Accordingly, this study examines the relationship between EASIX and mortality risk among patients with AF. METHODS: This retrospective analysis utilized data from the Medical Information Marketplace in Intensive Care IV (MIMIC-IV) database, which includes critically ill patients diagnosed with AF. To examine the association between EASIX scores and mortality, Kaplan-Meier survival analysis, Cox proportional hazards models, and restricted cubic spline regression were applied to evaluate the relationship between EASIX and all-cause mortality. Subgroup analyses were conducted to explore potential interactions with key patient characteristics, and sensitivity analyses were performed to further confirm the robustness of the results. RESULTS: A total of 3,193 patients were included in the analysis. KM survival analysis showed that elevated EASIX levels were associated with a higher risk of both in-hospital and ICU mortality. After adjusting for potential confounders, increased EASIX levels remained significantly associated with in-hospital mortality [HR, 1.09 (95% CI 1.03, 1.15), P = 0.0002] and ICU mortality [HR, 1.10 (95% CI 1.04, 1.17), P = 0.0002]. Stratified analyses revealed a significant interaction between sepsis, respiratory failure, and EASIX in relation to both in-hospital and ICU mortality. To evaluate the robustness of the findings, a sensitivity analysis was performed. After additionally adjusting for metoprolol and heparin as covariates, patients in the highest EASIX group continued to demonstrate the greatest mortality risk: the HR for in-hospital death was 2.08 (95% CI: 1.51-2.85), and the HR for ICU death was 1.83 (95% CI: 1.21-2.65). CONCLUSION: Elevated EASIX levels correlate with higher mortality rates, underscoring its potential as an accessible tool for identifying high-risk patients and informing clinical decisions. However, further studies are needed to explore the underlying mechanisms and validate its applicability across diverse patient populations.