Admission Endothelial Activation and Stress Index in Acute Myocardial Infarction: Incremental Value Beyond the GRACE Score and a Test of the Index Weights

Background/Objectives: The Endothelial Activation and Stress Index (EASIX), calculated from lactate dehydrogenase, creatinine and platelet count, has been linked to mortality in cardiovascular cohorts. We examined whether admission EASIX adds prognostic information to the Global Registry of Acute Coronary Events (GRACE) score for in-hospital mortality in acute myocardial infarction (AMI), and whether its fixed weights are supported. Methods: We retrospectively studied consecutive adults with AMI undergoing coronary angiography; patients with an estimated glomerular filtration rate below 30 mL/min/1.73 m2 were excluded. EASIX was modelled on the log2 scale. Incremental value was assessed against a GRACE model refitted in this cohort and against the published GRACE risk after recalibration, by discrimination, calibration, decision curves and bootstrap validation. Results: In-hospital death occurred in 225 of 4777 patients (4.7%). Each doubling of EASIX was associated with mortality after adjustment for the GRACE score (odds ratio 2.386, 95% confidence interval 2.053–2.774) and after clinical adjustment (2.363, 1.974–2.828). Adding EASIX raised the area under the curve from 0.855 to 0.890 (optimism-corrected increment 0.034, 95% confidence interval 0.025–0.052) and improved the Brier score and net benefit. Added to the recalibrated published GRACE risk, EASIX raised the area under the curve from 0.856 to 0.881 (corrected increment 0.024, 0.012–0.040). Findings were consistent in both infarct types. Freely estimated weights differed from the fixed weights but added little discrimination. Conclusions: Admission EASIX was independently associated with in-hospital mortality in AMI and added discrimination and net benefit to both a refitted and the published GRACE risk. External validation is required before clinical use.