Genotyping GUided Antiplatelet theRapy in pAtieNts Treated With Drug Eluting stEnts (GUARANTEE)

Inclusion Criteria: * Patient ≥18 years of age * Patient presents with acute coronary syndrome (ACS) or stable coronary artery disease (SCAD) * Patient has a percutaneous coronary intervention (PCI) indication and the new generation drug eluting stent(s) is successfully implanted Exclusion Criteria: * Patient unable to receive 12 months of dual anti-platelet therapy * Patient developing procedure-related complications such as stent thrombosis, coronary dissection, coronary perforation, cardiac tamponade or no-reflow during PCI * Contraindicated or allergic to clopidogrel or ticagrelor * Patient or physician refusal to enroll in the study * Patient having received thrombolytic therapy within the previous 24 hours * Physician has known the patient's CYP2C19 genotype * Anticipated discontinuation of dual anti-platelet therapy within the 12-month follow-up period, example for elective surgery * History of intracranial hemorrhage * Patient has a history of bleeding diathesis or coagulopathy * Patient has an active pathological bleeding, such as active gastrointestinal (GI) bleeding * Patient is pregnant, breastfeeding, or planning to become pregnant within 12 months * Patient is receiving chronic oral anticoagulation therapy (i.e., vitamin K antagonist, direct thrombin inhibitor, Factor Xa inhibitor) * Patient with cardiogenic shock or mechanical circulatory assist devices placed * Patient with LVEF \<30% * Patient with active liver diseases * Patient with severe renal insufficiency (eGFR \<30ml/min/1.73m2 based on simplified MDRD equation or CrCl \<30ml/min based on Cockcroft-Gault equation) * Patient has a malignancy or a life expectancy of less than one year * Platelet count \<100 000/μL, or hematocrit \<32% or \>52%, or white blood cell count \<3000/μL