Impact of Pre-Hospital Heparin Loading in STEMI Patients for Primary PCI: The HELP-PCI 2 Trial

Inclusion Criteria: 1. Age ≥18 years old; 2. STEMI within 12 hours of onset Newly developed adjacent two or more leads with ST segment elevation of ≥1mm (lead V2-V3 elevation of ≥2mm). Newly developed left bundle branch block (LBBB). In the right bundle-branch block (RBBB), the ST segment of leads V1-V3 is elevated or Q waves occur. 3. Primary PCI was planned if the time from first medical contact to balloon dilatation was expected to be less than 120 minutes. Exclusion Criteria: 1. Thrombolytic therapy recipients; 2. Currently taking oral anticoagulant drugs or having been treated with heparin, low molecular weight heparin, suldaparinol sodium, bivalirudin or IIb/IIIa receptor antagonists within 48 hours before randomization; 3. Patients undergoing cardiopulmonary resuscitation; 4. Patients with cardiogenic shock; 5. Combined mechanical complications (rupture of the free wall of the heart, perforation of the ventricular septum, insufficiency or rupture of the papillary muscle leading to severe mitral regurgitation); 6. History of intracranial parenchymal aneurysm, intracranial arteriovenous malformation, intracranial hemorrhage, ischemic stroke or transient ischemic attack within the last 6 months, and active hemorrhage within the last 2 weeks; 7. Major surgery within one month; 8. Previous history of CABG; 9. Patients with a history of heparin-induced thrombocytopenia or those known to be allergic to anticoagulant or antiplatelet drugs; 10. Combined with other serious diseases and life expectancy less than 12 months; 11. Pregnant or lactating women; 12. Currently participating in clinical research on other drugs or devices; 13. Refuse to sign the informed consent form; 14. The researcher judged that it was not suitable to participate in this study.