A research blood sample will be required to determine platelet activity which has to be taken > 2hours from the standard Clopidogrel pre-PCI loading. For most patients this will be taken in the catheter laboratory around the PCI procedure. In a few patients who are loaded with Clopidogrel close to the PCI procedure the blood samples may be taken in the ward or recovery area. Depending on the platelet activity results patients will be either entered into the registry or randomly allocated to either Clopidogrel or Prasugrel.