Clopidogrel plays a pivotal role in the antithrombotic regimen after percutaneous intervention with stent implantation. However, response to clopidogrel shows a wide interindividual variability and a high on-treatment residual ADP-inducible platelet reactivity has already been associated with an increased risk for adverse events after coronary stenting. In the present study, platelet reactivity will be determined by 6 different platelet function tests in patients on dual antiplatelet therapy after angioplasty and stenting for peripheral, coronary and carotid artery disease. One hundred patients showing high on-treatment residual ADP-inducible platelet reactivity in 2 or more tests will be randomized to receive either 75mg or 150mg of daily clopidogrel in addition to aspirin for 3 months. The aim of the present study is to investigate the effects of intensified antithrombotic therapy (150mg clopidogrel + 100mg aspirin daily) versus standard antithrombotic therapy (75mg clopidogrel + 100mg aspirin daily) in patients with decreased clopidogrel-mediated platelet inhibition after percutaneous intervention with stent implantation.

Inclusion Criteria:

• written informed consent
• angioplasty and stenting for peripheral, coronary or carotid artery disease

Exclusion Criteria:

• known aspirin or clopidogrel intolerance
• therapy with vitamin K antagonists (warfarin, phenprocoumon, acenocoumarol)
• treatment with ticlopidine, dipyridamol or nonsteroidal antiinflammatory drugs
• family or personal history of bleeding disorders
• malignant paraproteinemias
• myeloproliferative disorders
• heparin-induced thrombocytopenia
• severe hepatic failure
• known qualitative defects in thrombocyte function
• major surgical procedure within one week before enrollment
• platelet count < 100.000 or > 450.000/µl
• hemoglobin < 8 g/dl