The purpose of this study is to establish the optimal strategy for side branch stenting in coronary bifurcation lesion.

The purpose of this study is to evaluate the relative efficacy and safety of conservative strategy compared to aggressive strategy for side branch stenting in coronary bifurcation lesion.

Inclusion Criteria:

• Parent vessel diameter stenosis > 75%
• Parent vessel diameter stenosis 50% - 75% with angina and/or objective evidence of ischemia in the non-invasive stress test
• The reference diameter of both branches more than 2.3 mm by visual estimation

Exclusion Criteria:

• Cardiogenic shock
• ST-elevation myocardial infarction within 48 hours of symptom onset
• Left ventricular dysfunction (echocardiographic left ventricular ejection fraction < 25%)
• Graft vessels
• Patients who have to receive clopidogrel due to other conditions
• Patients who have to receive warfarin, cilostazol or other antiplatelet therapy
• Hypersensitivity to clopidogrel or aspirin
• Expectant survival less than 1 year
• Women who plan to become pregnant
• Patients with bleeding diathesis (coagulopathy, thrombocytopenia or platelet dysfunction, Gastrointestinal or genitourinary bleeding within the prior 3 months)
• Patients who are actively participating in another drug or device investigational study, which have not completed the primary endpoint follow-up period.