IMPROVE-STEMI: pPCI Plus Low-dose r-SK in STEMI

This is a multicenter, prospective, pragmatic, randomized controlled trial (IMPROVE-STEMI) aiming to evaluate the efficacy and safety of intracoronary low-dose recombinant streptokinase combined with primary percutaneous coronary intervention (pPCI) in patients with acute ST-segment elevation myocardial infarction (STEMI). A total of 3,300 patients will be enrolled, consisting of a core randomized study (300 patients, 1:1 ratio to pPCI + recombinant streptokinase vs. pPCI alone) and an extended observational study (3,000 patients receiving pPCI + recombinant streptokinase). The primary outcome measure is the coronary angiography-derived index of microcirculatory resistance (caIMR) immediately after the procedure. Secondary outcomes include the incidence of major adverse cardiovascular events (MACE) at 1 year, TIMI flow grade, corrected TIMI frame count (CTFC), and myocardial salvage index. The study duration is 24 months after the first patient enrollment, with follow-up visits scheduled at Day 5, Week 4, Week 12, Week 24, and Week 52.

Inclusion Criteria: 1. Patients diagnosed with acute ST-segment elevation myocardial infarction (STEMI) according to the guidelines. 2. Onset of STEMI symptoms within 12 hours. 3. TIMI thrombus grade ≥ 2. 4. Age 18 to 75 years, inclusive, gender (male or female). 5. Written informed consent obtained from the patient or their legal representative. Exclusion Criteria: 1. Pregnant or breastfeeding women. 2. Severe cardiovascular diseases, including cardiogenic shock, cardiac rupture, or acute aortic syndrome (e.g., aortic dissection, coronary artery dissection, or aneurysm) that cannot be excluded. 3. Known coronary artery disease unsuitable for revascularization. 4. Previously known severe heart disease. 5. Patients with ventricular fibrillation requiring cardiopulmonary resuscitation or refractory to 3 electrical defibrillation attempts. 6. Continuous oral anticoagulant use for ≥ 3 months. 7. High risk of bleeding or other contraindications to thrombolytic therapy. 8. Body weight \< 40 kg or \> 200 kg. 9. Allergy to recombinant streptokinase or contrast agents. 10. Other systemic diseases, including life expectancy \< 1 year due to other diseases, severe liver or kidney dysfunction, hematological diseases, acute pancreatitis, diabetic retinopathy, consciousness disorders, or malignant tumors. 11. Any condition that the investigator considers unsuitable for participation in this study.