The purpose of ZEST-LATE (Evaluation of the Long-term Safety After Zotarolimus-Eluting Stent, Sirolimus-Eluting Stent, or PacliTaxel-Eluting Stent Implantation for Coronary Lesions - Late Coronary Arterial Thrombotic Events) trial is to assess the relationship between long-term clopidogrel use beyond 1 year and long-term rates of death or MI after DES implantation and to estimate the duration of dual antiplatelet therapy for preventing the late thrombotic events.

Prospective, two arms, open-labeled, randomized multi-center trial of approximately 2,000 patients enrolled at 19 centers in Korea. Among all patients enrolled in the ZEST (Comparison of the Efficacy of Zotarolimus-Eluting Stent versus Sirolimus-Eluting Stent versus PacliTaxel-Eluting Stent for Coronary Lesions) trial, event-free patients who survived the first 12 months without nonfatal MI or repeat revascularization will be randomized to discontinue clopidogrel therapy at 12 months after DES implantation. All patients will be followed for another 12 months.

Inclusion Criteria:

1. Among the participants in the ZEST trial, event-free patients who survived the first 12 months without nonfatal MI or repeat revascularization
2. The patient or guardian agrees to the study protocol and the schedule of clinical follow-up, and provides informed, written consent, as approved by the appropriate Institutional Review Board/Ethical Committee of the respective clinical site.

Exclusion Criteria:

1. Contraindication to antiplatelet therapy
2. Non-cardiac co-morbid conditions are present with life expectancy <1 year or that may result in protocol non-compliance (per site investigator's medical judgment).
3. Patients who are actively participating in another drug or device investigational study, which have not completed the primary endpoint follow-up period.
4. Bleeding diathesis
5. Recent stroke within 6-months
6. Concurrent organ damage (creatinine level > 2.0mg/dL or AST and ALT > 3 times upper normal reference values)
7. Patients with left main stem stenosis (>50% by visual estimate)