Receiver operating characteristic–derived thresholds for early validation of myocardial injury in a rat ischemia-reperfusion model

Background Myocardial infarction (MI) is a major manifestation of cardiovascular disease and a leading cause of morbidity and mortality worldwide. In experimental research, rat ischemia-reperfusion (IR) model is widely used to evaluate cardioprotective strategies for translational and clinical purposes. However, early confirmation of successful MI induction often relies on subjective intraoperative observations, and objective criteria for verifying myocardial injury early after IR remain poorly standardized, potentially limiting reproducibility and leading to unnecessary loss of time and resources. This study aimed to establish objective early indicators of myocardial injury following IR surgery in rats and to derive preliminary receiver operating characteristic (ROC)-based diagnostic thresholds for early confirmation of cardiac injury. Methods Rats subjected to IR or sham surgery were evaluated during the first postoperative days using blood biochemistry and echocardiography. Based on functional, hemodynamic, and histological assessments performed at day 56, a subgroup of IR-operated animals with preserved cardiac function and minimal fibrosis was classified as non-injured and served as the reference group for subsequent ROC analyses. Results and discussion Cardiac troponin I (cTnI) emerged as a reliable threshold marker for distinguishing animals with significant cardiac injury, exceeding > 12,000 ng/L within 24 h after injury. Lactate dehydrogenase (LDH) and aspartate aminotransferase (AST) also demonstrated reliable threshold values for identifying significantly injured animals (> 780 U/L, > 960 U/L, respectively). In parallel, echocardiography revealed threshold-based evidence of early systolic dysfunction in injured animals, with reduced fractional shortening (≤ 35%,( fractional area change (≤ 55%) and ejection fraction (≤ 70%), providing functional confirmation of impaired cardiac performance. Together, these ROC-derived thresholds provide a preliminary practical panel of biomarkers and echocardiographic parameters for early in vivo identification of myocardial injury following IR in rats, with the potential to improve experimental consistency and facilitate early model validation.