Long-term Clinical Outcomes of intraVascular Ultrasound-guided vs Angiography-guided Primary pErcutaneous Intervention in Patients With Acute ST Segment Elevated Myocardial Infarction

Inclusion Criteria: * Clinical inclusion criteria: 1. Age \> 18 years 2. Onset of STEMI \> 30 minutes, but \< 12 hours 3. ST segment elevation in at least 2 contiguous leads of≥ 1mm or newly developed LBBB on ECG 4. Willing and able to provide informed consent * Angiographic inclusion criteria: 1. Having at least one infarct-related coronary artery, of which (1) the Culprit lesion is suitable for stenting (2) the reference diameter of culprit vessel is ≥ 2.5 mm but ≤ 4 mm (3) the TIMI flow is ≤ 1 in culprit lesion segment prior to guide wire crossing 2. No excessive tortuosity and calcification in the culprit lesion segment that allowing stent implantation Exclusion Criteria: * Clinical exclusion criteria: 1. Contraindicating to any concomitant study medications 2. Having cardiogenic shock with hemodynamic instability 3. A history of bleeding diathesis or known coagulopathy 4. 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 5. Planned surgery which may cause discontinuation of ADP-receptor antagonist 6. Other serious illness (e.g., cancer) that may reduce life expectancy to less than 1 year 7. Repeated MI within 7 days of hospitalization for acute MI * Anigographic Exclusion Criteria: 1. Bifurcated lesion unable to identify the culprit lesion 2. The culprit lesion is located in the left main artery 3. Diffusive lesions without distinguishable culprit lesion 4. Previous stent implantation in the culprit lesion segment or STEMI caused by stent thrombosis 5. Likely CABG procedure within 30 days 6. Renal failure requiring or during dialysis