Eligibility Criteria:
Inclusion Criteria:
* Age 18-74 years
* Patients with acute coronary syndrome undergoing PCI with stenting
* Sinus rhythm
* Written informed consent
Exclusion Criteria:
* Known hypersensitivity to prasugrel or ticagrelor
* Requirement for oral anticoagulant prior to the Day 30 visit
* Any previous history of ischemic stroke, intracranial hemorrhage or disease (neoplasm, arteriovenous malformation, aneurysm)
* Any active bleeding or history of gastrointestinal bleeding, genitourinary bleeding or other site abnormal bleeding within the previous 3 months, other bleeding diathesis, or considered by investigator to be at high risk for bleeding
* Concomitant oral or IV therapy with strong CY P3A inhibitors (ketoconazole, itraconazole, voriconazole, telithromycin, clarithromycin, nefazodone, ritonavir, saquinavir, nelfinavir, indinavir, atazana vir, grapefruit juice N1 L/d), CYP3A substrates with narrow therapeutic indices (cyclosporine, quinidine), or strong CYP3A inducers (rifampin /rifampicin, phenytoin, carbamazepine).
* Increased risk of bradycardiac events.
* Dialysis required.
* Severe uncontrolled chronic obstructive pulmonary disease
* Known severe hepatic impairment
* Pregnancy or breastfeeding
* Left ventricular ejection fraction \< 45%, severe left ventricular hypertrophy, diastolic dysfunction, severe valve disease
* Prior myocardial infarction, percutaneous coronary intervention or coronary artery bypass grafting
* Weight \< 60 Kg
* Alcohol or narcotics abuse
* Major periprocedural complications: death, cardiogenic shock, stent thrombosis, arrhythmias requiring cardioversion/defibrillation, temporary pacemaker insertion or intravenous antiarrhythmic agents, respiratory failure requiring intubation, retroperitoneal bleeding, major bleeding (need for blood transfusion or drop in haemoglobin post-PCI by ≥ 5 gr/ dl or intracranial bleeding), unsuccessful PCI (residual stenosis \> 30% or flow \< ΤΙΜΙ 3) or planned staged PCI in the next 5 days after randomization
* Any residual stenosis \> 40% in LAD
* Small vessels or diffuse coronary atherosclerosis
* Inability to detect coronary blood flow in LAD