This is a prospective, single-center, randomized trial including 1500 subjects requiring PCI. Subjects with ischemic heart disease due to stenotic lesions in either native coronary arteries or coronary artery bypass undergoing PCI with stent placement and no contraindication to prolonged dual antiplatelet therapy (≥1 year) are eligible to be in the study. Subjects will be randomized to either guided antiplatelet therapy arm (n=750) or standard therapy arm (n=750) and undergo laboratory testing, antiplatelet adjustment, and clinical follow-up for 1 year.