OCT Study of the MGuard Prime Stent in Patients With Heart Attacks

Inclusion Criteria: * Subject is \>18 years of age. * Subject is experiencing clinical symptoms consistent with acute myocardial infarction (AMI) of \>30 minutes and ≤12 hours in duration. * ST-segment elevation ≥1 mm per lead in ≥2 contiguous leads is present in at least one ECG prior to consent. * Subject agrees to all required follow-up procedures and visits. * Subject provides written, informed consent. * The target lesion is a single de novo lesion in a native coronary artery. * Based on coronary anatomy, PCI is indicated for the culprit lesion with anticipated use of stenting. * TIMI flow of 0/1 is present at baseline and TIMI flow of 2/3 is present prior to randomization. * The reference vessel diameter (RVD) of the infarct lesion is 2.75-4.0 mm by visual assessment, assessed after TIMI 2/3 flow is restored. * The entire lesion length requiring treatment is ≤33 mm by visual assessment, assessed after TIMI 2/3 flow is restored. Exclusion Criteria: * Currently enrolled in another investigational device or drug trial that has not reached the primary endpoint or that clinically interferes with the current study endpoints. * A previous coronary interventional procedure of any kind within 30 days - - - Female patients of childbearing potential. * Subject undergoing cardiopulmonary resuscitation (patients in whom cardiopulmonary resuscitation was successfully performed and in whom normal mental status was achieved, may be enrolled). * Cardiogenic shock (SBP \<80 mmHg for \>30 minutes, or requiring IV pressors or intra-aortic balloon bump (IABP) or other hemodynamic support device for hypotension). * Prior administration of thrombolytic therapy for the current admission * Concurrent medical condition with a life expectancy of less than 12 months. * History of cerebrovascular accident or transient ischemic attack within the last 6 months, or any permanent neurologic deficit * Prior intracranial bleed at any time, or known intracranial pathology (e.g. tumor, arteriovenous malformation, or aneurysm). * Active or recent major bleeding within 6 months. * History of bleeding diathesis or coagulopathy or inability to accept blood transfusions. * Known hypersensitivity or contraindication to i) aspirin; or ii) heparin and bivalirudin; or iii) clopidogrel, prasugrel and ticagrelor; or iv) cobalt or nickel; or v) contrast media, which cannot be adequately pre-medicated (prior anaphylaxis, however, is an absolute contraindication to enrollment). * Known calculated creatinine clearance \<30 mL/min, hemoglobin \<10 g/dL or platelet count \<150,000 for the present admission or within 7 days prior to index procedure, if available. NOTE: Baseline labs do not have to be available to consent patient. If laboratory results become available only after randomization, and do not meet inclusion and exclusion criteria, the patient will not be de-registered from the study. * Surgery planned or any other reason necessitating discontinuation of dual anti-platelet therapy (aspirin and an ADP antagonist) within 6 months. * Rheolytic thrombectomy, a PTCA balloon with diameter \>2.0 mm, or any other device (other than guide wire or simple manual aspiration) is required to restore TIMI 2/3 flow in the infarct vessel. * Unprotected left main stenosis ≥50% or planned left main intervention. * Any non-study lesion in the infarct artery with visually estimated diameter stenosis ≥50% and reference vessel diameter ≥2.0 mm or that will require treatment during the index procedure. * Multi-vessel or multi-lesion intervention required during the index procedure. * Excessive tortuosity, calcification or diffuse distal disease is present either proximal to, at or distal to the target lesion making it unlikely that the OCT catheter or stent will be able to reach or can be deployed across the target lesion with full expansion. * Target lesion is a bifurcation with a side branch ≥2.0 mm in diameter. * Target lesion is at the site of or within a vessel with a previously implanted stent. * Target lesion is within a bypass graft conduit, or can only be reached by passing the study stent through a bypass graft conduit. * Aortic dissection or mechanical complication of STEMI (papillary muscle rupture, ventricular septal defect or free wall rupture with or without pseudoaneurysm) identified by left ventriculography or any other modality (such as echocardiography, MRI, CT, physical exam).