Differential Effect of Ticagrelor Versus Prasugrel on the Adenosine-induced Coronary Vasodilatory Responses in Patients With Acute Coronary Syndrome Undergoing Percutaneous Coronary Intervention

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