Previous randomized clinical trials have deomonstrated the efficacy and safety of short-term dual antiplatelet therapy (DAPT) after percutaneous coronary intervention (PCI), however, the single antiplatelet agent to be maintained after short-term DAPT was different. Therefore, which antiplatelet agent to be maintained after short-term DAPT needs further invstigations.

The investigators hypothesized that short-term (1-3 months) DAPT followed by clopidogrel monotherapy will be superior to short-term DAPT followed by aspirin monotherapy after PCI in patients with ischemic heart disease. We will evaluate whether clopidogrel monotherapy will reduce the rate of net adverse clinical events (NACE) at 12 months compared to aspirin monotherapy after very-short term DAPT. Eligible patients will be randomized to short-term DAPT followed by clopidogrel monotherapy or short-term DAPT followed by aspirin monotherapy at hospitalization for index PCI. Randomization will be stratified according to 1) bleeding risk (high bleeding risk [HBR] or non-HBR), 2) clinical presentation (acute coronary syndrome or chronic coronary artery disease), and 3) lesion complexity (non-complex or complex lesion). Regarding the duration of very-short term DAPT, the maintenance duration of DAPT (1-month or 3-month) will be determined as follows:

• If the patients are at HBR (HBR is defined according to ARC-HBR criteria: meeting at least 1 major or 2 minor criteria), 1-month DAPT will be given regardless of clinical presentation or lesion complexity.
• In the patients are at non-HBR, 3-month DAPT will be given in those treated for unstable angina and/or complex lesions (complex lesion is defined as meeting at least one of the following: number of stents implanted ≥3, number of lesions treated ≥3, 3-vessel treated, bifurcation PCI with 2 stents, total stent length ≥60mm, or chronic total occlusion).

Inclusion Criteria:

1. Patients ≥19 years
2. Patients who received new generation zotarolimus-eluting Onyx stents implantation for treating ischemic heart disease
3. Provision of informed consent

Exclusion Criteria:

1. Age ≥ 85 years
2. Acute myocardial infarction

2. Left main bifurcation requiring 2-stent technique 3. Pregnant women or women with potential childbearing 4. Life expectancy < 1 year 5. Inability to follow the patient over the period of 1 year after enrollment, as assessed by the investigator 6. Inability to understand or read the informed consent