This study is aimed to investigate if the bivaliruding with prolonged full dose infusion after PCI is superior to heparin alone in reducing 30-day mortality or major bleeding for patients with STEMI treated with emergency PCI. A total of 6000 STEMI patients will be enrolled and randomly assigned to receive bivalirudin or heparin during emergency PCI in a 1:1 ratio. This study will provide key evidence for peri-operative anticoagulant therapy decisions in STEMI patients.

Inclusion Criteria:

• Any age;
• STEMI patients undergoing primary PCI with ST elevation≥1mm in≥2 contiguous leads or new LBBB with symptom onset 48h;
• Patients requiring staged revascularization of non-culprit vessels within 30 days may be enrolled. In such cases the same antithrombotic agents and PCI procedures must be used in the staged procedure consistent with the index procedure PCI, in particular the assigned antithrombin agent heparin vs. bivalirudin);
• Dual antiplatelet drugs must be administrated according to guidelines before PCI (loading doses and maintenance doses of aspirin and clopidogrel or ticagrelor);
• The subject or legal representative has been informed of the nature of the study, understood the provisions of the protocol, was able to ensure adherence, and signed informed consent.

Exclusion Criteria:

• Not suitable for emergency primary PCI;
• STEMI treated by thrombolysis;
• Patients received heparin, LMWH, fondaparinux, bivalirudin, or GPI within 48 hours before the index PCI;
• Mechanical complications (such as ventricular septal rupture, papillary muscle rupture with acute mitral regurgitation, etc.);
• Known allergy or contraindications to heparin, bivalirudin, aspirin, or both clopidogrel and ticagrelor
• Patients in whom the investigators consider inappropriate to participate in this study (eg, have participated in another drug/instrument study or undergoing another drug/instrument study).