The elderly represent a growing segment of the coronary population treated by dual antiplatelet therapy for percutaneous coronary intervention (PCI). These patients bear a higher risk of both ischemic events and bleeding complications than younger patients, with a subsequently higher rate of mortality.Recentprogress in antithrombotic treatment demonstrated the efficacy of adding a P2Y12 receptor antagonist to low-dose aspirin. Whether this benefit is also present in the elderly remains a debated issue due to the lack of specific data in this sub-population. The present study was realized to provide specific data on platelet response to clopidogrel, standard dose (75 mg) or prasugrel 5 mg in elderly patients (≥75 years old) whereas the superiority in PR response of the latter should allows the Prasugrel therapy in elderly patients with the better clinical efficacy and therapeutical safety already showed compared with Clopidogrel.

Inclusion Criteria:

• Acute coronary syndrome
• PCI with stent implantation
• clopidogrel responsiveness
• > 75 years of age.

Exclusion Criteria:

• history of bleeding diathesis
• chronic oral anticoagulation treatment
• contraindications to antiplatelet therapy
• PCI or coronary artery bypass grafting (CABG) < 3 months
• hemodynamic instability
• platelet count < 100,000/μl
• hematocrit < 30%
• creatinine clearance < 25 ml/min
• Patients with a history of stroke
• other contraindication for prasugrel administration
• patients weighing < 60 kg
• high on treatment platelet reactivity