Prasugrel in Comparison to Clopidogrel for Inhibition of Platelet Reactivity in Patients With ST-elevation Myocardial Infarction (STEMI)

Inclusion Criteria: 1. Age ≥18 years old 2. Patients with STEMI undergoing primary PCI with stenting 3. Platelet reactivity in PRU ≥235 2 hours post 600 mg clopidogrel loading dose 4. Informed consent obtained in writing Exclusion Criteria: 1. Treatment with other investigational agents (including placebo) or devices within 30 days prior to randomization or planned use of investigational agents or devices prior to the Day 5. 2. Pregnancy 3. Breastfeeding 4. Inability to give informed consent or high likelihood of being unavailable until Day 5. 5. Cardiogenic shock 6. Major periprocedural complications (death, stent thrombosis, vessel perforation, arrhythmias requiring cardioversion, temporary pacemaker insertion or intravenous antiarrhythmic agents, respiratory failure requiring intubation, vascular injury (pseudoaneurysm, arteriovenous shunt, retroperitoneal bleeding or hematoma \>5 cm at the arterial catheter insertion site), major bleeding (need for bood transfusion or drop in haemoglobin post-PCI by ≥ 5 gr/ dl or intracranial bleeding). 7. Unsuccessful PCI (residual stenosis \> 30% or flow \< ΤΙΜΙ 3) or planned staged PCI in the next 5 days after randomization 8. Requirement for oral anticoagulant prior to the Day 5 9. Current or planned therapy with other thienopyridine class of ADP receptor inhibitors. 10. Known hypersensitivity to prasugrel or ticagrelor 11. History of gastrointestinal bleeding, genitourinary bleeding or other site abnormal bleeding within the previous 6 months. 12. Other bleeding diathesis, or considered by investigator to be at high risk for bleeding on thienopyridine therapy. 13. Any previous history of ischemic stroke, intracranial hemorrhage or disease (neoplasm, arteriovenous malformation, aneurysm). 14. Thrombocytopenia (\<100.000 / μL) at randomization 15. Anaemia (Hct \<30%) at randomization 16. Polycythaemia (Hct \> 52%) at randomization 17. Periprocedural IIb/IIIa inhibitors administration 18. Severe allergy to contrast agent, unfractionated heparin, enoxaparin or bivalirudin that cannot be adequately premedicated. 19. Recent (\< 6 weeks) major surgery or trauma, including GABG. 20. Subjects receiving daily treatment with nonsteroidal anti-inflammatory drugs (NSAIDs) or cyclooxygenase-2 (COX-2) inhibitors that cannot be discontinued for the duration of the study. 21. INR\>1.5 at randomization