Aspirin 50mg vs 100mg Combined With P2Y12 Inhibitor After PCI

Inclusion Criteria: * Aged 18 to 85 years at the time of screening * Diagnosed with acute coronary syndrome (ACS) or chronic coronary syndrome (CCS) * Has undergone successful percutaneous coronary intervention (PCI) with stent implantation * Planned to receive at least 12 months of dual antiplatelet therapy (DAPT) with aspirin plus a P2Y12 inhibitor after PCI * Able to provide written informed consent and comply with study follow-up requirements Exclusion Criteria: * Known hypersensitivity or contraindication to aspirin, P2Y12 inhibitors, or related excipients * High bleeding risk: history of intracranial hemorrhage, gastrointestinal bleeding within 6 months, active bleeding diathesis, or coagulopathy * Severe hepatic dysfunction (Child-Pugh class C) or severe renal impairment (eGFR \< 30 mL/min/1.73 m²) * Ischemic or hemorrhagic stroke within 3 months before enrollment * Pregnant or lactating women; women of childbearing potential unwilling to use effective contraception * Life expectancy \< 12 months due to other severe comorbidities such as advanced malignancy * Participation in another interventional clinical trial within 30 days before screening * Any other condition judged by the investigator to make the patient unsuitable for the study