Association Between Eosinophil-to-Monocyte Ratio and ST-Segment Resolution in Young STEMI Patients Undergoing Primary...

Impaired myocardial reperfusion after primary percutaneous coronary intervention (pPCI) is associated with adverse outcomes in ST-segment elevation myocardial infarction (STEMI). This study investigated the relationship between the eosinophil-to-monocyte ratio (EMR) and ST-segment resolution in young patients with STEMI undergoing pPCI.

This retrospective, single-center study included 492 consecutive patients with STEMI younger than 45 years who underwent pPCI between January 2022 and January 2026. The primary endpoint was incomplete ST-segment resolution (<70%), while no-reflow was evaluated as a secondary endpoint. Univariable and multivariable logistic regression, restricted cubic spline, and receiver operating characteristic (ROC) analyses were performed.

Lower EMR was associated with greater thrombus burden, impaired postprocedural Thrombolysis in Myocardial Infarction (TIMI) flow, increased glycoprotein IIb/IIIa inhibitor use, incomplete ST-segment resolution, and no-reflow (all P < 0.001). Incomplete ST-segment resolution occurred in 52 patients (10.6%), no-reflow in 25 (5.1%), and in-hospital death in 1 (0.2%). Lower EMR remained independently associated with incomplete ST-segment resolution (odds ratio [OR] 0.245, 95% confidence interval [CI] 0.127-0.475, P < 0.001). In a secondary analysis, lower EMR was associated with no-reflow (adjusted OR 0.079, 95% CI 0.021-0.238, P < 0.001). Restricted cubic spline analysis showed a nonlinear inverse association between EMR and impaired myocardial reperfusion. EMR demonstrated acceptable discriminatory performance for incomplete ST-segment resolution (area under the curve [AUC] 0.757) and no-reflow (AUC 0.827).

Lower admission EMR was associated with impaired myocardial reperfusion in young patients with STEMI undergoing pPCI. EMR may represent an admission reperfusion-associated marker, but its biological and clinical significance remains uncertain and requires prospective external validation.