Associations and prognostic implications of myocardial tissue injury stages in ST-elevation myocardial infarction using the Canadian Cardiovascular Society classification

Abstract Background Myocardial infarction (MI) involves progressive tissue damage beyond necrosis. The recently proposed Canadian Cardiovascular Society (CCS) classification defines this damage in four stages, potentially optimizing personalized risk stratification and advancing research on cardioprotective treatments. The baseline associations and prognostic implications of this classification remain to be explored. Objectives To compare clinical characteristics across CCS stages and to validate their prognostic implications in patients with ST-elevation myocardial infarction (STEMI) treated by percutaneous coronary intervention (PCI). Methods We analysed 1,109 STEMI patients included in three prospective studies. Cardiac magnetic resonance (CMR) imaging was performed 3 (interquartile range 2-5) days after MI and patients were classified as follows: stage 1 (aborted MI), stage 2 (MI with necrosis and absence of microvascular injury), stage 3 (MI with necrosis and microvascular obstruction) and stage 4 (MI with necrosis and intramyocardial haemorrhage). Results This analysis revealed distinct patterns of clinical presentation, biomarker profiles and cardiac function at different CCS stages. There were differences in adverse clinical event rates and mortality between CCS stages (major adverse cardiovascular event [MACE]: 0.7%, 3.4%, 3.1%, 15.7%, p