The primary objective of this prospective clinical registry is to determine the prevalence and level of thienopyridine resistance seen in a population undergoing contemporary percutaneous coronary intervention (PCI) or coronary artery bypass surgery (CABG).

This is a prospective cohort study of 1000 patients presenting to the Washington Hospital Center for percutaneous coronary intervention or coronary artery bypass surgery.

The aim of this prospective clinical registry is to determine the prevalence and level of thienopyridine resistance seen in a population presenting for cardiac catheterization and undergoing percutaneous coronary intervention (PCI) or coronary artery bypass surgery (CABG). Thienopyridine resistance will be measured by flow cytometry of the vasodilator-stimulated phosphoprotein (VASP) phosphorylation, and/or the VerifyNow P2Y12 assay, and/or the Chrono-Log Lumi-Aggregometer, and/or the PlaCor PRT 7000 platelet reactivity assay.

A secondary objective of this study is to correlate a variety of genetic polymorphisms with levels of platelet reactivity.

Inclusion Criteria:

1. Patient >18 years old.
2. PCI group only: Patient scheduled to undergo cardiac catheterization or underwent percutaneous coronary intervention (PCI), during hospital stay.
3. CABG group only: Patient is scheduled to undergo, or has underwent, coronary artery bypass surgery with at least one saphenous vein graft.
4. Treated with a loading dose of clopidogrel or prasugrel at least 6 hours prior to the blood draw, or on a maintenance dose of clopidogrel or prasugrel for a minimum of 5 days.
5. Genetic testing subgroup only: Patient has undergone PCI (only), and has been treated with a thienopyridine as in 4.

Exclusion Criteria:

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

1000 patients, male or female, older than 18 years of age, who are scheduled for or underwent percutaneous coronary intervention (PCI) or CABG and have been treated with a loading dose of a thienopyridine or on a maintenance dose of a thienopyridine.