Patient undergoing PCI in whom at least one DES is implanted and in whom PCI of all treated lesions is successful (diameter stenosis <30% with TIMI 3 flow in all treated lesions) without major complications (defined as freedom from procedural death, intraprocedural stent thrombosis, procedural myocardial infarction or sustained vessel closure, or need for emergency bypass graft surgery).

Inclusion Criteria:

1. Patients undergoing PCI in whom at least one DES is implanted and in whom PCI of all treated lesions is successful (diameter stenosis <30% with TIMI 3 flow in all treated lesions) without major complications (defined as freedom from procedural death, intra-procedural stent thrombosis, procedural myocardial infarction or sustained vessel closure, or need for emergency bypass graft surgery). One or more bare metal stents (BMS) may be implanted, and other lesions may be treated without stenting as long as at least one DES is implanted. However, the procedure must be successful and uncomplicated (as defined above) for all lesions (DES + BMS + non-stent).
2. Aspirin use: Adequate aspirin loading given prior to PCI: at least 300 mg non enteric coated oral aspirin at least 6 hours prior to the procedure or 324 mg chewed or 250 mg IV aspirin at least 30 minutes prior to the procedure.
3. Patient has Hematocrit between 33 and 52% and Platelet Count between 119,000 and 502,000/µl.
4. For US sites: Only FDA-approved DES stents may be used in this study. For OUS sites: Only DES stents that are CE marked for approval may be used in this study.
5. PCI performed with unfractionated or low molecular weight heparin, or bivalirudin as the procedural antithrombin.
6. Patient or guardian able to provide informed written consent.

Exclusion Criteria:

1. Patients in whom blood for Accumetrics VerifyNow platelet function testing cannot be drawn after the minimum clopidogrel loading duration and Glycoprotein (GP) IIb/IIIa inhibitor washout duration as follows:

   1. Clopidogrel loading: Clopidogrel loading pre PCI is recommended, but post PCI clopidogrel loading is acceptable per standard of care. In all patients (whether or not clopidogrel is initiated pre or post PCI), prior to blood drawing for VerifyNow platelet function testing, a 600 mg loading dose must have been given at least 6 hours prior, or a 300 mg loading dose must have been given at least 12 hours prior, or the patient must have been maintained on at least 75 mg of clopidogrel daily for at least 5 days.
   2. GP IIb/IIIa inhibitor washout: Eptifibatide or tirofiban must have been discontinued for at least 24 hours prior to VerifyNow platelet function testing. Abciximab must have been discontinued for at 10 days prior to VerifyNow platelet function testing.
2. Severe allergy to stainless steel, contrast dye, all anti-thrombin agents (unfractionated and low molecular weight heparin and bivalirudin), aspirin or clopidogrel that cannot be adequately pre-medicated.
3. Current enrollment in an investigational drug or device study that has not reached the time period of the primary endpoint.
4. Patients in whom bypass graft surgery is planned within 2 years.
5. Patients with stent thrombosis before the performance of pre-discharge VerifyNow platelet function testing.
6. Patients unwilling or unable to complete clinical follow-up for the duration of the study.