The Study to Assess AMI Treated With Balloon Angioplasty.

Inclusion Criteria: 1. Have prolonged, continuous (lasting at least 20 minutes) chest pain despite administration of nitrates and onset within 12 hours of randomization, and one of the following: 1. ST segment elevation \>=1mm in standard leads and \>=2mm in 2 or more contiguous precordial leads with reciprocal ST depression 2. New or presumably new left bundle branch block (LBBB) 2. The culprit lesion must be identified on a de novo native coronary artery and an emergency angioplasty must be possible. The culprit site must be visualized before the stent implantation; Exclusion Criteria: 1. Killip class \> 2 upon arrival to the cath-lab; 2. Significant (\>50%) stenosis proximal or distal to the target lesion that might require revascularization or impede inflow or runoff; 3. Evidence of massive thrombus in the infarct related artery distally to the culprit lesion; 4. Documented left ventricular ejection fraction \<=30%; 5. Target lesion is located in an arterial or venous by-pass graft; 6. ECG documented evidence of prior myocardial infarction; 7. Patient who received thrombolytic therapy for the current AMI before enrollment in this study.