OPTIMIZE-APT: Tailored Versus Conventional Antiplatelet Therapy After Intravascular Imaging-guided Drug-eluting Stent Implantation

Inclusion Criteria: 1. Men or women ≥19 years 2. Typical chest pain or objective evidence of myocardial ischemia suitable for PCI 3. Significant de novo coronary artery lesions suitable for DES implantation 4. Patients who underwent optimized stent implantation either by IVUS or OCT * Using IVUS * MSA \>5.5 mm2, or MSA \>90% of the MLA at the distal reference segment * Plaque burden \<50% with 5 mm of both stent edge * No edge dissection; thrombus or plaque protrusion occupying \< 10% of the stent area * Using OCT * MSA \>4.5 mm2, or MSA \>90% of the MLA at the distal reference segment * No significant malapposition * No significant edge dissection†; thrombus or plaque protrusion occupying \< 10% of the stent area (\*Significant malapposition is defined as strut separation ≥ 0.3 mm from the vessel wall extending over a length \> 3 mm. †Significant dissection is defined as a dissection penetrating the medial layer and extending over more than one quadrant.) 5. 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. Angiographic exclusion criteria: any of the followings 1. Bypass graft lesions 2. Lesions in which impaired delivery of imaging catheters is expected: * Extreme angulation (≥90°) proximal to or within the target lesion. * Excessive tortuosity (≥ two 45° angles) proximal to or within the target lesion. * Heavy calcification proximal to or within the target lesion. 2. In-stent restenosis 3. Hypersensitivity or contraindication to device material and its degradants and cobalt, chromium, nickel, platinum, tungsten, acrylic and fluoro polymers that cannot be adequately pre-medicated. 4. Persistent thrombocytopenia (platelet count \<80,000/μl) 5. Any history of hemorrhagic stroke or intracranial hemorrhage / TIA or ischemic stroke within the past 6 months 6. A known intolerance or hypersensitivity to a study drug (aspirin, clopidogrel or ticagrelor) or heparin 7. Patients requiring long-term oral anticoagulants or cilostazol 8. Any surgery requiring general anesthesia or discontinuation of aspirin and/or an ADP antagonist is planned within 12 months after the procedure. 9. A diagnosis of cancer (other than superficial squamous or basal cell skin cancer) in the past 3 years or current treatment for the active cancer. 10. Any clinically significant abnormality identified at the screening visit, physical examination, laboratory tests, or electrocardiogram which, in the judgment of the Investigator, would preclude safe completion of the study. 11. History of liver cirrhosis (Child-Pugh B or C) or biliary tract obstruction 12. Life expectancy \< 1 years for any non-cardiac or cardiac causes 13. Cardiogenic shock at the index admission 14. Patient's pregnant or breast-feeding 15. Active bleeding or extreme-risk for major bleeding (e.g. active peptic ulcer disease, gastrointestinal pathology with a high risk for bleeding, malignancies with a high risk for bleeding) 16. Unwillingness or inability to comply with the procedures described in this protocol.