Local Matrix Metalloproteinase 9 Level Determines Early Clinical Presentation of ST-Segment–Elevation Myocardial Infarction

OBJECTIVE—Early clinical presentation of ST-segment–elevation myocardial infarction (STEMI) and non–ST-segment–elevation myocardial infarction affects patient management. Although local inflammatory activities are involved in the onset of MI, little is known about their impact on early clinical presentation. This study aimed to investigate whether local inflammatory activities affect early clinical presentation. APPROACH AND RESULTS—This study comprised 94 and 17 patients with MI (STEMI, 69; non-STEMI, 25) and stable angina pectoris, respectively. We simultaneously investigated the culprit lesion morphologies using optical coherence tomography and inflammatory activities assessed by shedding matrix metalloproteinase 9 (MMP-9) and myeloperoxidase into the coronary circulation before and after stenting. Prevalence of plaque rupture, thin-cap fibroatheroma, and lipid arc or macrophage count was higher in patients with STEMI and non-STEMI than in those with stable angina pectoris. Red thrombus was frequently observed in STEMI compared with others. Local MMP-9 levels were significantly higher than systemic levels (systemic, 42.0 [27.9–73.2] ng/mL versus prestent local, 69.1 [32.2–152.3] ng/mL versus poststent local, 68.0 [35.6–133.3] ng/mL; P