Simple indices of infarct size post ST-Elevation Myocardial Infarction (STEMI) provides similar risk stratification to cardiac MRI

Introduction: Myocardial Infarct Size (IS) determined soon after ST-segment elevation myocardial infarction (STEMI) has prognostic significance, and can be assessed by cardiac biomarker levels, electrocardiographic (ECG) parameters, and imaging modalities (including echocardiography and cardiac magnetic resonance imaging [CMRI]).

Objectives and methods: We evaluated methods of IS assessment, 12-lead ECG Selvester QRS scores and high-sensitivity Troponin T (hsTnT) levels measured ≥48hr (plateau phase of hsTnT elevation), compared to paired CMRIs and echocardiograms, in a prospective cohort of patients with STEMI undergoing percutaneous coronary intervention (PCI) during the index hospitalisation. Associations were determined between IS, as assessed by these methods, and 24-month major adverse cardiac events (MACE), a hierarchical composite of: death, stroke and hospitalization for heart failure.

Results: Of 233 patients undergoing early CMRI after STEMI, 211 patients (86% male; 54% anterior MI) had first STEMIs, median age 56 years [interquartile range 50-64], of whom 165 (78%) underwent primary PCI and 46 (22%) pharmaco-invasive PCI. Ejection fraction improved from 48% [42-54] acutely to 52% [44-60] at 2 months (p< 0.05). Plateau phase hsTnT levels, QRS scoring and CMRI-determined IS post-STEMI correlated for anterior MIs (all comparisons r>0.4, p<0.01); highest tertiles of these 3 parameters predicted 24 month MACE (log-rank <0.01). Multi-variable binary logistic regression analysis showed 72h hsTnT levels predicted 24-month MACE (p<0.01).

Conclusion: Post-PCI treatment of STEMI, hsTnT levels measured ≥48h and Selvester QRS scoring correlated with CMRI-determined IS. These parameters predicted MACE at 24 months and should be routinely assessed for post-STEMI risk stratification.