The primary purpose of this study is to compare the efficacy and safety of antiplatelet monotherapy with aspirin or clopidogrel for 2 years in patients who have not experienced MACE (major adverse cardiac events) including all-cause death, acute coronary syndrome including non-fatal MI (myocardial infarction), or urgent revascularization under combined antiplatelet therapy for 12 ± 6 months after PCI (percutaneous coronary intervention) with DES (drug-eluting stents). The trial tests the hypothesis that clopidogrel is superior to aspirin in preventing clinical events and device-oriented outcomes. Clinical events are defined as a composite of all-cause death, non-fatal MI, stroke, readmission due to acute coronary syndrome (ACS), or Bleeding Academic Research Consortium (BARC) class ≥ 3.29 Device-oriented outcomes include target lesion/vessel revascularization (TLR/TVR) and Academic Research Consortium (ARC)-defined stent thrombosis.

The primary endpoint of this study is the rate of clinical events defined as a composite of MACE and major bleeding complications. MACE includes all-cause death, non-fatal MI, stroke, and readmission due to ACS (acute coronary syndrome). Major bleeding is defined as bleeding (BARC class ≥ 3) at 24 months. Non-fatal MI is defined as any confirmed evidence of myocardial necrosis in a clinical setting consistent with myocardial ischemia without resulting in death, which is supported by electrocardiography, cardiac enzymes, or cardiac imaging according to the third Universal Definition of MI.37, 38 A readmission due to ACS is defined as any re-hospitalization definitely originating from an ACS event, which satisfies the definition of the American College of Cardiology Foundation and the American Heart Association.37, 39 A stroke is defined as any abrupt-onset, non-convulsive, focal, or global neurological deficit lasting more than 24 hours, which is caused by ischemia or hemorrhage in the brain.39 Secondary endpoints are the rate of device-oriented outcomes including TLR/TVR and stent thrombosis at 24 months, and minor gastrointestinal (GI) complications with the related cost-effectiveness. TLR is defined as any repeat revascularization procedure at the original lesion of the index procedure any time during the follow-up period.40 TVR is defined as any repeat revascularization procedure involving at least one of the target vessels that were treated in the index procedure.40 Stent thrombosis is defined according to the ARC.41, 42 Minor GI complications are assessed on the basis of newly developed GI symptoms, newly added GI medications, or symptom-driven GI endoscopy. At each visit, clinicians will question the patient regarding GI symptoms from intermittent epigastric soreness or bloating due to melena/hematochezia. Any additional GI medications, including H2-blockers and proton pump inhibitors, will be documented for each patient. If a patient undergoes endoscopy, the type of endoscopy, test results, and further interventions will be recorded. Additional medical costs related to these minor GI complications (South Korean won/year) will be calculated to assess the cost effectiveness of each drug based on average Korean expenses. All endpoints will be assessed primarily by the investigator and adjudicated secondarily by the independent clinical event committee.