This is a single-centre, open-label prospective randomized pharmacodynamic investigation of 2 antiplatelet regimens in patients undergoing coronary intervention for ST segment elevation myocardial infarction(STEMI):

1. Tirofiban bolus only or bolus followed by 2 hour infusion on top of 600 mg clopidogrel or 60 mg prasugrel.
2. Prasugrel given at 60 mg.

Primary hypothesis: Percentage IPA after 20uMol/ADP at 30' will be superior in the tirofiban arm (as aggregate) versus prasugrel alone arm Percentage IPA at 30' after 20uMol/ADP 90%±15 and 80%±15 in the tirofiban and prasugrel alone arm, respectively. For a power of 90% and an alpha error set at 5%, 50 patients per group have to be recruited.

Inclusion Criteria:

• Chest pain for >30 min with an electrocardiographic ST-segment elevation more than 1 mm in two or more contiguous electrocardiogram (ECG) leads, or with a new left bundle-branch block, and admission either within 12 h of symptom onset or between 12 and 24 h after onset with evidence of continuing ischemia

Exclusion Criteria:

• Administration of fibrinolytic or any GP IIbIIIa inhibitors for the treatment of current AMI or within 1 month before history of bleeding diathesis
• Known sensitivity to abciximab, to any component of the product or to murine monoclonal antibodies
• Major surgery or trauma within 30 days
• Active bleeding
• Previous stroke in the last six months
• Oral anticoagulant therapy
• Pre-existing thrombocytopenia
• Vasculitis
• Hypertensive retinopathy
• Severe hepatic failure
• Severe renal failure requiring haemodialysis
• Documented allergy/intolerance or contraindication to clopidogrel or inability to assume clopidogrel on a consecutive daily basis for a minimum of 30 days, or to heparin or aspirin
• Uncontrolled hypertension (systolic or diastolic arterial pressure >180 mmHg or 120, respectively, despite medical therapy)
• Limited life expectancy, e.g. neoplasms, others
• Inability to obtain informed consent