Safety of 6-month Duration of Dual Antiplatelet Therapy After Acute Coronary Syndromes (SMART-DATE)

Inclusion Criteria: 1. Subject must be ≥ 20 years. 2. Subject is able to verbally confirm understandings of risks, benefits and treatment alternatives of receiving percutaneous coronary intervention and he/she or his/her legally authorized representative provides written informed consent prior to any study related procedure. 3. Subject must have a culprit lesion in a native coronary artery with significant stenosis (\>50% by visual estimate) eligible for stent implantation. 4. Subject must have clinical diagnosis of ACS that includes unstable angina and MI. The specific definitions of ACS, as follows; 1) ST-segment elevation MI (STEMI) : elevation of ST-segment more than 0.1 mV in 2 or more contiguous electrocardiographic (ECG) leads or new left bundle-branch block with elevated biomarkers of myocardial necrosis 2) Non-ST-segment elevation MI (NSTEMI) : Elevated biomarkers of myocardial necrosis (troponin or CK-MB \> upper reference limit) with one of the following; (a) Transient ST-segment elevation or depression, or T-wave changes consistent with myocardial ischemia, (b) Identification of a culprit lesion at coronary angiography 3) Unstable angina : An accelerating pattern or recurrent episodes of chest pain at rest or with minimal effort and new ST-segment depression of at least 0.05 mV, or T wave inversion of at least 0.3 mV in at least 2 leads. The ECG criteria for unstable angina were based on the TACTICS-TIMI 18 trial. 5. Target lesion(s) must be located in a native coronary artery with visually estimated diameter of ≥ 2.25 mm and ≤ 4.25 mm. 6. Target lesion(s) must be amenable for percutaneous coronary intervention Exclusion Criteria: 1. The patient has a known hypersensitivity or contraindication to any of the following medications: Heparin, Aspirin, Clopidogrel, Biolimus, Everolimus, Zotarolimus, and Contrast media (Patients with documented sensitivity to contrast media which can be effectively premedicated with steroids and diphenhydramine \[e.g. rash\] may be enrolled. Those with true anaphylaxis to prior contrast media, however, should not be enrolled.) 2. Patients with active pathologic bleeding 3. Gastrointestinal or genitourinary bleeding within the prior 3 months, or major surgery within 2 months. 4. Systemic (intravenous) Biolimus, everolimus, zotarolimus use within 12 months. 5. Female of childbearing potential, unless a recent pregnancy test is negative, who possibly plan to become pregnant any time after enrollment into this study. 6. History of bleeding diathesis, known coagulopathy (including heparin-induced thrombocytopenia), or will refuse blood transfusions 7. Noncardiac comorbid conditions are present with life expectancy \<1 year or that may result in protocol noncompliance (per site investigator's medical judgment). 8. An elective surgical procedure is planned that would necessitate interruption of clopidogrel during the first 12 months post enrollment. 9. Patients who are actively participating in another drug or device investigational study, which have not completed the primary endpoint follow-up period.