This study evaluates the efficacy and safety of tailored antithrombotic therapy with early (<6-month post-PCI) intensified (low-dose ticagrelor [120 mg loading, then 60 mg bid maintenance] and aspirin) and late (>6-month post-PCI) deescalated (clopidogrel alone) strategy in patients undergoing high-risk complex PCI as compared with standard Dual Antiplatelet Therapy(aspirin and clopidogrel for 12 months).

Inclusion Criteria:

1. Age 19 and more

2. Subjects who scheduled for percutaneous coronary intervention(PCI) with contemporary drug-eluting stent

3. Patients must have at least one of any features of complex high-risk anatomic, procedural, or clinical-related factors;

   • Clinical factors: diabetes, chronic kidney disease (i.e. creatinine clearance <60 mL/min), or low left ventricular ejection fraction (<40%) or
   • Lesion- or procedure-related factors: left main PCI, chronic total occlusion, bifurcation lesion requiring two-stent technique, severe calcification, diffuse long lesion (lesion length ≥ at least 30 mm), multi-vessel PCI (≥ 2 vessels requiring stent implantation), ≥3 requiring stent implantation, ≥ 3 lesions will be treated, or predicted total stent length for revascularization > 60 mm

4. The patient or guardian agreed to the study protocol and the schedule of clinical follow-up and provided informed, written consent, as approved by the appropriate institutional review board/ethical committee of the respective clinical site.

Exclusion Criteria:

1. Enzyme-positive Acute myocardial infarction (non-ST-elevation myocardial infarction (NSTEMI) or ST Elevation Myocardial Infarction (STEMI))

2. Contraindication to aspirin or P2Y12 inhibitors (ticagrelor or clopidogrel)

3. Use of Gp IIb/IIIa inhibitors at randomization

4. Cardiogenic shock

5. Treatment with only bare-metal stent (BMS) or balloon angioplasty during the index procedure.

6. Requirements for chronic oral anticoagulation (warfarin or Non-vitamin K antagonist oral anticoagulant (NOACs))

7. 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)

8. History of intracranial hemorrhage or intracranial aneurysm

9. Planned surgery within 180 days

10. Severe liver disease (ascites and/or coagulopathy) or Dialysis-dependent renal failure at screening

11. Platelet count <80,000 cells/mm3 or hemoglobin level <10 g/dL

12. At risk of bradycardia (subjects with sinus node dysfunction or atrioventricular block more than 2nd degree but without a permanent pacemaker)

13. Use of strong cytochrome P-450 3A inhibitor or inducers within 2 week of the date of enrollment

    : ketoconazole, clarithromycin, nefazodone, ritonavir, atazanavir, rifampin/rifampicin, rifabutin, dexamethasone, phenytoin, carbamazepine, phenobarbital

14. Pregnant and/or lactating women.

15. Concurrent medical condition with a life expectancy of less than 1 years

16. Active participation in another investigational study of a drug or device that has not completed the primary endpoint or follow-up period

17. Inability to provide written informed consent or participate in long-term follow-up