Utility of CMR markers of myocardial injury in predicting LV functional recovery: results from PROTECTION AMI CMR sub study

Background: Adverse left ventricular (LV) remodelling following acute ST-segment elevation myocardial infarction (STEMI) has prognostic importance. We aimed to predict 90-day left ventricular (LV) function following acute STEMI using variables from clinical presentation, biomarkers, and cardiovascular magnetic resonance imaging (CMR). Methods: Consecutive patients undergoing primary percutaneous coronary intervention for anterior STEMI as part of the Selective Inhibition of Delta-protein Kinase C for the Reduction of Infarct Size in Acute Myocardial Infarction (PROTECTION-AMI) trial were enrolled into the CMR sub-study at selected sites. CMR was performed at baseline (days 3 to 5) and 90 days and used to evaluate infarct size, myocardial salvage index, infarct heterogeneity, microvascular obstruction and global LV function. Biochemical markers including creatinine kinase area under the curve (CK AUC), peak CK, peak CK-myocardial band (CK-MB) and AUC, and troponin I were collected at specific time-points. Results: Ninety-six patients were enrolled in the CMR sub study and 85 completed the 90-day follow-up, across 24 centres worldwide. LV ejection fraction (EF) was 56% (46-63%) at baseline and 60% (49-67%) at 90 days (p<0.001). Infarct size had moderate inverse correlation with 90-day EF (Spearman's rho. =. -0.7, p < 0.001) and had the strongest correlation when compared to myocardial salvage index (Spearman's rho. =. 0.5, p. =. 0.001), infarct heterogeneity (Spearman's rho. =. -0.4, p. =. 0.02 or microvascular obstruction (Spearman's rho. =. -0.4, p. <. 0.001). All biochemical markers had similar moderate relationship to LVEF at 90 days (Spearman's rho -0.6 to -0.8, p=0.001). In a multivariable model, only baseline LVEF, CMR infarct size and infarct heterogeneity independently predicted 90-day LVEF. Conclusion: This study reports findings of a combined CMR protocol (including myocardial oedema imaging) in a multi-centre, multi-vendor setting. We found infarct size, infarct heterogeneity and myocardial salvage index correlated favourably with 90-day LVEF, however only the former two were independently predictive.