In patients with heart attacks, the treatment of choice is to restore blood flow with percutaneous coronary intervention (PCI) (use of stents (metal meshes) to open blockages). After PCI, the standard drug treatment includes aspirin and clopidogrel. These medications block full function of the platelet cells, which are responsible for clotting. Despite their use, patients after PCI are at risk for heart attacks, sudden clotting of stents or death. A major contributor may be resistance to clopidogrel. New more potent drugs, which can overcome the resistance, are now available; however, they come with an increase chance of severe bleeding and costs. An ideal solution would be to identify at-risk patients and selectively treat them with more potent drugs, while lower-risk patients continue with clopidogrel. This type of strategy (personalized strategy) would decrease heart attacks and death (compared to clopidogrel), while also preventing bleeding complications (compared to treating all patients with the new drugs).