Aspirin and a PoTent P2Y12 Inhibitor Versus Aspirin and Clopidogrel in Patients Undergoing PCI for Complex Lesion

Inclusion Criteria: * ① Subject must be at least 19 years of age * ② Subject who can verbally confirm understandings of risks, benefits and treatment alternatives and he/she or his/her legally authorized representative provides written informed consent prior to any study related procedure * ③ Patients undergoing elective PCI as follows: 1. True bifurcation lesion (Medina 1,1,1/1,0,1/0,1,1) with side branch ≥2.5 mm size 2. Chronic total occlusion (≥3 months) as target lesion 3. PCI for unprotected left main disease (left main ostium, body, or distal bifurcation including non-true bifurcation lesions) 4. Long coronary lesions (expected stent length ≥38 mm) 5. Multi-vessel PCI (≥2 vessels treated at one PCI session) 6. Multiple stent needed (≥3 stents per patient) 7. In-stent restenosis lesion as target lesion 8. Severely calcified lesion (encircling calcium in angiography) 9. Ostial lesions of left anterior descending artery, left circumflex artery, or right coronary artery Exclusion Criteria: * ① Hemodynamic instability or cardiogenic shock * ② Subjects with serious bleeding (Intracerebral hemorrhage, gastrointestinal bleeding, hematuria, hemoptysis, and etc.) * ③ Previous history of intracerebral hemorrhage, transient ischemic attack, or stroke * ④ Known hypersensitivity or contraindications to study medications (aspirin, clopidogrel, and prasugrel) * 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 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) * ⑦ Patients presenting with biomarker positive acute coronary syndrome * ⑧ Patients chronically taking prasugrel or ticagrelor (≥1 week) * ⑨ Subjects ≥75 years of age or \<60 kg of body weight * ⑩ Patients taking warfarin or novel oral anticoagulants (dabigatran, rivaroxaban, edoxaban, or apixaban) * Eligible patients will be randomly assigned to treatment arms, stratified by participating centers, presence of diabetes mellitus, and stent types.