Rapid Activity of Platelet Inhibitor Drugs Study 2

50 consecutive patients with STEMI undergoing PPCI with bivalirudin (GP IIb/IIIa not allowed) will be randomized to receive Prasugrel (n= 25) or Ticagrelor (n= 25) before PPCI ( primary percutaneous coronary intervention) in a open label fashion. The loading dose of Prasugrel will be 60 mg, the loading dose of Ticagrelor will be 360 mg in 25 patients. The loading dose will be performed as soon as possible in the Emergency Room or in the Cath Lab. In the case of vomit in the first hour after drug loading dose a new reduced loading dose will be administered (30 mg Prasugrel or 180 mg Ticagrelor). All interventions will be performed by the femoral approach according to current standards. The use of thrombectomy before infarct-related artery stenting, of everolimus eluting stent and of closure devices will be strongly encouraged. Bivalirudin will be administered as a bolus 0.75 mg/kg followed by 1.75 mg/kg/h infusion during PCI. After PCI (percutaneous coronary intervention) a reduced bivalirudin infusion of 0.25 mg/kg/h for 4 hours will be allowed. Dual antiplatelet therapy (100 mg aspirin associated with 5 or 10 mg Prasugrel or 180 mg Ticagrelor) will be recommended for 12 months. Residual platelet reactivity will be assessed in all patients at baseline (time of LD), and after 1, 2, 4 and 12 hours by a point-of-care test VerifyNow bedside available in the Intensive cardiac care Unit. High residual platelet reactivity will be defined as a Platelet Reactivity Units (PRU) \> 240 by VerifyNow. At the same time point, Aspirin Reactivity Units (ARU) by VerifyNow will be also assessed. Follow-up will be performed by outpatient visits or telephone interviews at 6 months.