We hypothesized that clopidogrel mono-therapy will not be inferior to the extended DAPT in terms of the occurrence of both ischemic and bleeding events, for lesions or patients at high risk for either ischemic or bleeding complications 12 months after drug-eluting stent (DES) implantation.

Patients at high risk for either ischemic or bleeding complications, but who were stable without clinical evetns for 12 months after DES implantation will be included in this study. Eligible patients will be randomized to continue DAPT (aspirin plus clopidogrel) for further 24 months or to change to single antiplatelet therapy with clopidogrel (clopidogrel-alone). Randomization will be stratified according to 1) clinical presentation (acute coronary syndrome or stable coronary artery disease) and 2) age (≥75 or <75). Baseline clinical and angiographic characteristics, laboratory findings will be assessed at the time of randomization. All patients will provide informed consent on their own initiative. All of study subjects will be have an outpatient visit as scheduled in outpatient clinic. Occurrence of study endpoints will be documented at clinical visit or telephone interview every 6 months up to 24 months after randomization. Antiplatelet drugs will be open-label and prescribed by attending physician.

Inclusion criteria (must all met)

1. Patients >19 years old
2. Patients who underwent DES implantation 12 months (-1 to +5 months) previously.
3. High risk characteristics (clinical or lesion) for ischemic events (must at least one)

High risk patients; clinical criteria

1. Acute coronary syndrome
2. Previous history of cerebrovascular accidents
3. History of peripheral artery intervention
4. Heart failure (left ventricular ejection fraction ≤40%)
5. Diabetes treated with medication
6. Chronic renal insufficiency including end-stage renal diseases

High risk lesions; angiographic or procedural criteria

1. Left main diseases
2. Bifurcation lesions
3. Chronic total occlusion
4. In-stent restenotic lesions
5. Graft lesions
6. Diffuse long lesions requiring total stent length ≥28 mm
7. Calcified lesions requiring atherectomy
8. Multivessel coronary artery disease with multiple stents
9. Small vessel disease requiring stent diameter of ≤2.5 mm

Exclusion criteria

1. Age> 80 years
2. Pregnant women or women with potential childbearing
3. Life expectancy < 1 year
4. Refusal or inability to understand of informed consent
5. Need for chronic oral anticoagulation
6. History of major bleeding within 3 months prior to randomization

Antiplatelet drugs will be open-label and prescribed by attending physician.