A Study Evaluating the Vascular Healing and Neointimal Transformation at 1 Month After Implantation of BioFreedom™ Drug-coated Stents and the Xience Drug-eluting Stent System in Patients With Acute Coronary Syndrome and High Bleeding Risk Using Optical Coherence Tomography

Inclusion Criteria: 1. Age ≥18 years 2. Male or non-pregnant female 3. Acute coronary syndrome (ACS) patients requiring percutaneous coronary intervention (PCI) 4. No contraindications for coronary artery bypass grafting (CABG) 5. High bleeding risk (HBR) patients per ARC-HBR definition (meeting ≥1 major or 2 minor criteria): Major Criteria: * Expected long-term oral anticoagulation * Severe/end-stage chronic kidney disease (eGFR \<30 mL/min) * Moderate/severe anemia (Hb \<110 g/L) * Spontaneous bleeding requiring hospitalization/transfusion within 6 months (or recurrent) * Chronic bleeding diathesis * Moderate/severe thrombocytopenia pre-PCI (platelet count \<100×10⁹/L) * Liver cirrhosis with portal hypertension * Active malignancy in past 12 months (excluding non-melanoma skin cancer; defined as diagnosis/treatment within 12 months) * History of spontaneous intracranial hemorrhage * Traumatic intracranial hemorrhage within 12 months * Known cerebral arteriovenous malformation * Moderate/severe ischemic stroke within 6 months * Major surgery/severe trauma within 30 days pre-PCI * Planned non-deferrable major surgery during dual antiplatelet therapy Minor Criteria: * Age ≥75 years * Moderate chronic kidney disease (eGFR:30\~59 ml/min) * Mild anemia (male: Hb=110\~129 g/L; female: Hb=110\~119 g/L) * Spontaneous bleeding requiring hospitalization/transfusion within 6-12 months pre-PCI * Chronic NSAID/steroid use post-PCI * Ischemic stroke \>6 months pre-PCI 6. Capable of understanding trial objectives and providing informed consent Angiographic Inclusion Criteria: 1. Target lesion must be primary native coronary artery lesion 2. Target lesion with ≥70% diameter stenosis (visual estimate), or 50-70% diameter stenosis (visual estimate) with ischemic evidence 3. ≥1 non-target lesion requiring intervention 4. Non-target lesions eligible for elective treatment within 1 month Exclusion Criteria: General Exclusion Criteria: 1. Presence of ≥1 evidence of heart failure including: * NYHA Class III or higher, or * Killip classification ≥ Grade 2, or * Left ventricular ejection fraction (LVEF) ≤30% within 30 days pre-procedure (by echocardiography or intraoperative ventriculography) 2. Cardiogenic shock patients 3. Known allergies to: Aspirin / clopidogrel / ticagrelor / heparin, Contrast agents/drugs used in drug-eluting stents or contraindications to aspirin/ clopidogrel / ticagrelor 4. Life expectancy \<12 months or factors potentially compromising clinical follow-up 5. Participation in other drug/medical device trials prior to enrollment without reaching primary endpoint timelines 6. History of substance abuse (alcohol/cocaine/heroin, etc.) 7. Severe arrhythmias (e.g., high-risk ventricular premature contractions/ ventricular tachycardia) 8. Other medical conditions deemed unsuitable by investigators Angiographic Exclusion Criteria: 1. Left main coronary artery disease 2. Bypass graft lesions 3. Evidence of extensive thrombus in target vessel