This study is being done to learn more about platelet reactivity (how well the small cells in the bloodstream work) in people who undergo Percutaneous coronary intervention (PCI) for stable and unstable (acute myocardial infarction) indications. Stable means you have not demonstrated any acute injury to your heart prior to your PCI; unstable means you have demonstrated some acute injury to your heart prior to your PCI. The investigators intend to determine if there is a change in platelet reactivity from the time of PCI to 30days post-PCI and does this change differ depending upon the conduction in which you present for PCI. This is going to be done with a variety of platelet reactivity assays.

Inclusion Criteria:

• Patient >18 years old.

• Patient scheduled to undergo PCI for either stable CAD or AMI:

• Stable CAD defined as negative cardiac isoenzymes prior to the PCI as well as no resting ECG changes indicative of ACS.

• AMI defined as positive cardiac isoenzymes prior to the PCI and/or resting ECG changes indicative of ACS.

  3. Patients treated with a loading dose of clopidogrel at least 6 hours prior to the blood draw or on a maintenance dose of clopidogrel (of at least 75mg QD) for a minimum of 5 days.

Exclusion Criteria:

• Known allergies to aspirin, clopidogrel, or prasugrel
• Use of a glycoprotein (GP) IIb/IIIa inhibitor within 8 hours of the blood draw;
• Patient known to be pregnant or lactating;
• Patient with known history of bleeding diathesis or currently active bleeding;
• Platelet count <100,000/mm the day of the blood draw;
• Hematocrit <25% the day of the blood draw;
• On warfarin therapy at the time of the blood draw or the need for warfarin therapy in the subsequent month following the blood draw;
• Known blood transfusion within the preceding 10 days of the blood draw;
• Patient who has received NSAID (not including ASA) within preceding 24 hours of the blood draw;
• Patients presenting with cardiogenic shock;
• Any significant medical condition, which in the investigator's opinion may interfere with the patient's optimal participation in the study.

Seventy five subjects (25 patients undergoing elective PCI for stable CAD and 50 patients undergoing urgent PCI for AMI(25 receiving clopidogrel and 25 receiving prasugrel - as determined by the treating physicians)