Microcirculatory Resistance After Primary Percutaneous Coronary Intervention Predicts Residual Myocardial Damage and Scar Formation

BACKGROUND: Coronary microvascular dysfunction has been associated with adverse cardiovascular events following acute myocardial infarction. This study evaluates the role of the angiography-derived index of microcirculatory resistance (angio-IMR) in predicting myocardial damage in patients with ST-segment–elevation myocardial infarction undergoing primary percutaneous coronary intervention (PCI). METHODS AND RESULTS: In this post hoc analysis of the CLEVER-ACS (Controlled-Level Everolimus in Acute Coronary Syndromes) trial, the associations between post-PCI angio-IMR of infarct-related coronary arteries (IRAs) and infarct size, microvascular obstruction, and left ventricular ejection fraction at 30 days as assessed by cardiac magnetic resonance were investigated. High post-PCI angio-IMR was defined as ≥40 mm Hg s. In non-IRAs, angio-IMR was measured before IRA-PCI. A total of 52 IRAs and 94 non-IRAs of 52 patients were analyzed. Post-PCI angio-IMR was 41.5 (interquartile range [IQR], 28.5–55.7) mm Hg*s in IRAs and pre-PCI angio-IMR was 43.7 (IQR, 31.7–54.0) mm Hg s in non-IRAs (P=0.70). Patients with high post-PCI angio-IMR (52%) exhibited a larger myocardial infarct size (36.0 [IQR, 23.0–52.5] g versus 14.5 [IQR, 6.50–26.5] g, P<0.001) and a lower left ventricular ejection fraction (46.5% [IQR, 39.5%–49.5%] versus 55.0% [IQR, 48.0%–61.4%], P=0.002) at 30 days as compared with those with low post-PCI angio-IMR values. Post-PCI angio-IMR positively correlated with myocardial infarct size (r=0.45, P=0.001) and extent of microvascular obstruction (r=0.40, P=0.004) at 30 days. Post-PCI angio-IMR predicted myocardial infarct size (area under the curve, 0.78 [IQR, 0.65–0.92]; P=0.001) and extent of microvascu-lar obstruction (area under the curve, 0.74 [IQR, 0.60–0.89]; P=0.009) at 30 days. CONCLUSIONS: In patients with ST-segment–elevation myocardial infarction, post-PCI angio-IMR was identified as independent predictor of myocardial infarct size and extent of microvascular obstruction.