BioFreedom™ is the world's first polymer-free drug-coated stent (DCS), utilizing a proprietary microstructured surface technology. Its abluminal microporous surface directly carries BA9™ (a sirolimus derivative) with high lipophilicity. This design mitigates inflammatory responses while promoting early vascular healing and reducing thrombotic risk. Extensive clinical evidence has validated BioFreedom™'s superior performance in high-bleeding-risk (HBR) populations. However, comprehensive assessments of neointimal coverage and quantitative neointimal transformation post-implantation remain insufficient. With advancements in ultra-high-resolution optical coherence tomography (OCT), detailed evaluation of coronary stent healing has become feasible. This study will employ OCT to comparatively assess vascular healing patterns-including neointimal transformation and strut coverage-in ACS patients with HBR receiving either the commercially available BioFreedom™ DCS or Xience drug-eluting stent system. The findings will provide multidimensional insights into the devices' post-implantation efficacy and safety profiles.

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