MGuard™ Prime Stent System Clinical Trial in Patients With Acute ST Elevation Myocardial Infarction

Inclusion Criteria: * Subject is more than 18 years of age * Subject is experiencing clinical symptoms consistent with acute myocardial infarction (AMI) of more than 30 minutes and less than 12 hours in duration. * ST elevation more than 2 mm per lead in more than 2 contiguous leads is present in one ECG prior to consent. * Subject agrees to all required follow-up procedures and visits. * Subject or legal representative provides written, informed consent. * The target lesion is a de novo lesion in a native coronary artery. * Based on coronary anatomy, PCI is indicated for the culprit lesion with anticipated use of stenting. * The reference vessel diameter (RVD) of the infarct lesion is 2.75 to 4.0 mm by visual assessment, assessed either at baseline (if direct stenting is planned), or after pre-dilatation or thrombus aspiration (if direct stenting is not planned). * The entire lesion length requiring treatment is less than 24 mm (able to be covered by a single study stent), assessed either at baseline (if direct stenting is planned), or after pre-dilatation or thrombus aspiration (if direct stenting is not planned) * TIMI flow of 2/3 is present prior to randomization (in case of baseline TIMI flow 0/1, blood flow must be restored). Exclusion Criteria: * Left bundle branch block (LBBB), paced rhythm, or other ECG abnormality interfering with assessment of ST-segment. * Currently enrolled in another investigational device or drug trial that has not completed the primary endpoint or that clinically interferes with the current study endpoints. * A previous coronary interventional procedure of any kind within 30 days prior to the procedure. * 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 less than 80 mmHg for more than other hemodynamic support device for hypotension). * The subject requires a staged procedure of the target vessel (including branches) within 12 months or of any non-target vessel within 7 days post-procedure. * The target lesion requires treatment with a device other than PTCA prior to stent placement (such as, but not limited to excimer laser, rotational atherectomy, etc.). Manual thrombus aspiration may be used per operator discretion, but rheolytic thrombectomy is only permitted for procedural complications after randomization. * Prior administration of thrombolytic therapy for the current admission * Co-morbid condition(s) that could limit the subject's ability to participate in the trial or to comply with follow-up requirements, or impact the scientific integrity of the trial. * 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 site of major bleeding within 6 months. * History of bleeding diathesis or coagulopathy or inability to accept blood transfusions. * Known hypersensitivity or contraindication to either i) aspirin, or heparin and bivalirudin; or ii) clopidogrel , ticlopidine, prasugrel and ticagrelor; or iii) cobalt or nickel; or iv) contrast media, which cannot be adequately pre-medicated (prior anaphylaxis, however, is an absolute contraindication to enrollment). * Known serum creatinine level more than 2.5 mg/dl, hemoglobin less than 10 g/dL or platelet count less than 150,000 for the present admission or within 7 days prior to index procedure, if available. * Surgery planned or any other reason necessitating discontinuation of dual anti-platelet therapy (aspirin and an ADP antagonist) within 12 months * Aortic dissection or mechanical complication of STEMI * Unprotected left main stenosis more than 50%. * Multi-vessel intervention required during the index procedure. * Excessive tortuosity, calcification or diffuse distal disease * A non-infarct lesion with stenosis more than 50% is present in the target vessel * Target lesion is a bifurcation with a side branch more than 2.0 mm in diameter. * Target lesion 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 * In the Investigator's opinion the lesion/vessel is unsuitable for treatment with the study stent for any reason. * The lesion requires use of atherectomy, thrombectomy (not including manual thrombus aspiration catheters), laser devices, or proximal or distal embolic protection devices prior to randomization. * Aortic dissection or mechanical complication of STEMI