Determinants and Prognostic Value of Early Gadolinium Enhancement-Derived Myocardial Salvage Index in STEMI

BACKGROUND: T2-weighted imaging is commonly used to measure myocardial salvage in reperfused myocardial infarction but is hindered by poor reproducibility and indistinct boundaries. Early gadolinium enhancement (EGE) emerges as an alternative for measuring the area at risk. This study aims to evaluate the determinants of the myocardial salvage index (MSI) derived from EGE and its prognostic implications. METHODS: We analyzed acute cardiac magnetic resonance scans of 453 reperfused patients with ST-segment–elevation myocardial infarction (mean age, 60±12 years; 389 men) from April 2017 to July 2023 at a single center retrospectively. EGE was collected at 3 minutes after contrast agent injection, where hyperintense areas (signal intensities > mean+2SD of remote myocardium) were considered as the area at risk, plus the hypointense core within. MSI was calculated as the ratio of salvageable myocardium to the area at risk. Major adverse cardiovascular events included cardiovascular death, hospitalization for heart failure, reinfarction, and unplanned revascularization for the target vessel. RESULTS: During a median follow-up of 3.2 years (interquartile range, 1.6–4.7 years), at least one major adverse cardiac event occurred in 91 participants (20.1%). The median MSI was 35.0% (interquartile range, 22.9–59.5%), with smaller MSI observed in patients with larger infarcts ( P <0.001). Linear regression identified prepercutaneous coronary intervention Thrombolysis in Myocardial Infarction flow (β=3.35, P <0.001) and microvascular obstruction (β=−11.92, P <0.001) as independent determinants of MSI. Multivariable Cox regression showed that every 10% increase in MSI was associated with a 32% reduction in major adverse cardiac event risk (hazard ratio, 0.68 [95% CI, 0.53–0.86]; P =0.001). A graded response was observed between MSI and cardiovascular death and reinfarction. MSI greater than the median was associated with nontarget vessel-related reinfarctions but not target vessel-related ones (nontarget, P =0.027; target vessel, P =0.36). Good reproducibility was reported with EGE-measured area at risk (intraobserver, intraclass correlation coefficient [ICC]=0.95; interobserver, ICC=0.89). CONCLUSIONS: EGE-derived MSI was associated with prepercutaneous coronary intervention Thrombolysis in Myocardial Infarction flow and microvascular injuries. It was an independent predictor of major adverse cardiac events. Our results highlight the prognostic potential of EGE imaging in acute myocardial infarction.