Associations and Prognostic Implications of Myocardial Tissue Injury Stages in ST-Elevation Myocardial Infarction Using the Canadian Cardiovascular Society Classification.

Aims: The recently proposed Canadian Cardiovascular Society (CCS) classification categorizes post-infarction tissue injury into four stages, potentially improving risk stratification and guiding cardioprotective strategies. Its clinical and prognostic relevance in ST-elevation myocardial infarction (STEMI) remains unclear. We aimed to compare clinical characteristics across CCS stages and validate their prognostic implications in STEMI.

Methods and results: 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).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<0.001 and mortality: 0.7%, 1.7%, 0.9%, 6.3%, p<0.001). The CCS stage had a moderate to good predictive value for MACE and mortality (AUC 0.74 [95% CI: 0.68-0.80], p<0.001 and AUC 0.71 [95% CI: 0.61-0.80], p<0.001) at 12 months, respectively. CCS stages were independently associated with MACE in multivariable Cox regression (HR: 2.18 [95% CI, 1.70-2.78], p<0.001).

Conclusion: This study describes clinical characteristics across CCS stages and provides insights into their prognostic implications in a large cohort of STEMI patients reperfused by PCI. These data should inform the use of CCS stages in future trial designs.