Platelet and leukocyte activation in the presence of heparin and high doses of aspirin and clopidogrel. Comparison of levels of platelet aggregation between healthy controls and subjects on antiplatelet agents for (A) arachidonic acid and (B) ADP-induced maximum percentage of platelet aggregation. (C) Thrombin generation induced by low and high concentrations of phospholipids in controls and patients on heparin. Patients on heparin had undetectable low phospholipid dose-induced thrombin generation. **P < .05 for 1-way analysis of variance between groups and post hoc Tukey test between patient and control groups and between patient groups subjected to low and high doses of phospholipid-induced thrombin generation. (D-F) Comparison between proximal and distal coronary site for levels of platelet CD62P, PM-Agg, and monocyte CD11b. *P < .05. Solid bars and error bars represent mean ±SD.