A-005 Differentiation of Myocardial Injury Etiologies Using the Long-T ITC Complex: First U.S. Report from the MERITnI Study

Abstract

Early and accurate differentiation of acute myocardial infarction (MI) from non-ischemic and chronic myocardial injury remains a diagnostic challenge in patients presenting with suspected acute coronary syndrome (ACS). While high-sensitivity cardiac troponin (hs-cTn) assays enable earlier detection of myocardial injury, additional biomarkers that reflect early release kinetics may improve discrimination between acute and chronic processes. Data on circulating long-T ITC complex concentrations in this setting are limited. We evaluated the early release profile of long-T ITC complex in comparison with hs-cTnT and hs-cTnI in patients presenting to the emergency department (ED) with suspected ACS. We analyzed consecutive patients enrolled in the Mindray hs-cTnI Assay Analytical and Clinical Evaluation for the Diagnosis and Risk Assessment of Myocardial Infarction (MERITnI; NCT05853042) trial who presented to the ED with suspected ACS. Lithium heparin plasma samples obtained at 0- and 2-hours were tested on the Mindray CL-1200i platform chemiluminescence immunoassay for long-T ITC complex, hs-cTnT, and hs-cTnI. Absolute concentrations and biomarker ratios (long-T ITC/hs-cTnT) were assessed. All patients were adjudicated by predetermined clinicians for MI or no MI according to the 4th universal definition of MI after review of all available medical records, including 12-lead ECG, echocardiography, angiography, Alinity hs-cTnI concentrations, and clinical presentation. Among 882 subjects, 47 (5.3%) had acute MI, including 2.7% type 1 MI and 2.7% type 2 MI, and 23.4% had non-MI injury. Median time from symptom onset to presentation was 3.0 hours. Long-T ITC complex concentrations were higher patients with type1 MI, acute non-MI injury and chronic myocardial injury compared to patients without myocardial injury. Patients with type 1 MI demonstrated significantly higher long-T ITC concentrations compared with those with non-MI myocardial injury. The long-T ITC/hs-cTnI ratio increased significantly between 0 and 2 hours in patients with type 1 MI and acute non-MI injury, but not in chronic injury. This finding suggests a more rapid early release of long-T ITC complex compared with hs-cTnT in early serial sampling. Neither absolute concentrations nor ratios distinguished type 1 MI from type 2 MI. Long-T ITC concentrations and the long-T ITC/hs-cTnT specific ratio can statistically differentiate type 1 myocardial infarction and acute non-MI myocardial injury from chronic myocardial injury based on the initial 0-hour blood draw at time of presentation.