 It is recommended that patients who have drug-eluting stents placed in their coronary arteries take aspirin and Plavix Clopidogrel for at least a year. Patients who stop taking these antiplatelet drugs or who have resistance to the antiplatelet effects of these drugs are at a higher risk of clots occurring inside the stents which may result in a heart attack. At the present time, it is unknown if increasing the doses of the antiplatelet agents is effective in overcoming this resistance. The purpose of this project is to identify patients with antiplatelet drug resistance and to test whether an increase in the Plavix Clopidogrel dose overcomes antiplatelet drug resistance. 