MINI-AMI: Minimizing Infarct Size With Impella 2.5 Following PCI for Acute Myocardial Infarction

Inclusion Criteria: * Age ≥ 18 years * Signed Informed Consent * Acute anterior STEMI with ≥2 mm of ST-segment elevation in 2 or more contiguous anterior leads or ≥ 4 mm in total in the anterior leads, OR, Large Inferior STEMI with ≥2 mm of ST-segment elevation in 2 or more inferior leads AND EITHER ≥1 mm ST-segment elevation in V1 OR ≥1 mm of ST-segment depression in ≥2 contiguous anterior leads (V1-V3) * Primary PCI performed within 5 hours of the onset of symptoms * Patient undergoing emergent primary PCI of one culprit lesion in one major native epicardial coronary vessel * Successful revascularization of the culprit native coronary artery with TIMI Flow Grade of 3 at the end of PCI Exclusion Criteria: * Cardiac arrest requiring CPR within 24 hours prior to enrollment * Current cardiogenic shock * Left Bundle Branch Block (new or old) * Atrial fibrillation * Known history of prior MI * Prior coronary artery bypass graft surgery * Known mural thrombus in the left ventricle or contraindication to left ventriculography * Presence of a mechanical aortic valve * Documented presence of moderate to severe aortic stenosis or moderate to severe aortic insufficiency. * Known history of severe kidney dysfunction. * Known contraindication to MRI (implanted metallic or magnetically activated device; claustrophobia, inability to hold breath for 15 seconds). * History of recent (within 1 month) stroke or TIA * History of bleeding diathesis or known coagulopathy (including heparin-induced thrombocytopenia), or will refuse blood transfusions. * Administration of fibrinolytic therapy within 24 hours * Known hypersensitivity or contraindication to any of the following: Heparin, pork or pork products; Aspirin, All of the following: Clopidogrel, Ticlopidine, Prasugrel * Contrast media Participation in the active treatment or follow-up phase of another clinical study of an investigational drug or device. * Severe peripheral arterial obstructive disease that would preclude the IMPELLA® System placement * Requirement to treat two or more culprit vessels during primary PCI, or plan for staged coronary revascularization (PCI or CABG) within the next 30 days. * Inability to place Impella within 6 hours of the onset of symptoms, should patient be randomized to this arm.