This is a randomized, prospective, open label study to determine the cost-effectiveness of genotype-guided antiplatelet therapy. Patients undergoing percutaneous intervention (PCI) with stent implantation, will be randomized either to genotype guided dosing of antiplatelet therapy or usual care. The study utilizes a novel genotyping device, SpartanRx, to determine CYP2C19 genotypes from a buccal swab sample with 1 hour turnaround time.