Inclusion Criteria:  -Clinical Inclusion (CI) Criteria: CI. Age > 18 years C2. Onset of STEMI > 30 minutes, but < 12 hours C3. ST segment elevation in at least 2 contiguous leads of≥ 1mm or newly developed LBBB on ECG C4. Willing and able to provide informed consent  Angiographic Inclusion (AI) Criteria (visual estimate) AI1. Having at least one infarct-related coronary artery of which the Culprit lesion is suitable for stenting the reference diameter of culprit vessel is ≥ 2.5 mm but ≤ 4 mm the TIMI flow is ≤ 1 in culprit lesion segment prior to guide wire crossing AI2. No excessive tortuosity and calcification in the culprit lesion segment that allowing stent implantation  Exclusion Criteria:  Clinical Exclusion (CE) Criteria CE1. Contraindicating to any concomitant study medications CE2. Having cardiogenic shock with hemodynamic instability CE3. A history of bleeding diathesis or known coagulopathy CE4. A history of cerebrovascular accident (CVA) or transient ischemic attack (TIA) within the past 6 months; or a history of intracranial tumor, aneurysm or arteriovenous malformations; or a history of active peptic ulcer or active gastrointestinal (GI) bleeding within the past 2 months; or planned major procedure within 6 weeks; or known platelet count < 100,000 /mm3 or Hb < 10 g/dL CE5. Planned surgery which may cause discontinuation of ADP-receptor antagonist CE6. Other serious illness (e.g., cancer) that may reduce life expectancy to less than 1 year CE7. Repeated MI within 7 days of hospitalization for acute MI Angiographic Exclusion (AE) Criteria (visual estimate) AE1. Bifurcated lesion unable to identify the culprit lesion AE2. The culprit lesion is located in the left main artery. AE3. Diffusive lesions without distinguishable culprit lesion AE4. Previous stent implantation in the culprit lesion segment or STEMI caused by stent thrombosis AE5. Likely CABG procedure within 30 days