The main objective of the project is to assess the long-term prognostic impact of residual platelet reactivity after optimal antiplatelet therapy in a large cohort of patients with acute coronary syndrome undergoing invasive strategy.

Follow-up length will be at least 24 months. The primary end-point of the study will be a composite of death, myocardial infarction, urgent target vessel revascularization, stent thrombosis or stroke.

This study is mainly based on a registry of 2000 consecutive patients with acute coronary syndrome who received invasive treatment and for whom platelet reactivity after clopidogrel treatment will be prospectively assessed.

In the acute phase, blood samples for platelet reactivity assessment will be obtained 12 to 18 hours from 600 mg clopidogrel loading. Platelet-rich plasma, obtained by centrifuging whole blood for 10 min at 200 g, was stimulated with 10 M adenosine 5'-diphosphate (ADP) and residual aggregation will be assessed using a APACT 4 light transmittance aggregometer. Platelet aggregation (according to the Born's method) will be evaluated considering the maximal percentage of platelet aggregation in response to stimulus. Patients with platelet aggregation by 10 µmol ADP ≥ 90th percentile of controls (70%) will be defined as non-responders. The assessment of platelet reactivity will be repeated at 6 months. The importance of concomitant aspirin resistance will be also evaluated in such of patients.

Inclusion Criteria:

• acute coronary syndrome
• invasive treatment

Exclusion Criteria:

• in-hospital death that was not due to stent thrombosis,
• anticipated poor compliance to dual antipletelet treatment for at least 6 months,
• premature discontinuation of clopidogrel therapy.

patients with acute coronary syndrome who received invasive treatment and for whom platelet reactivity after clopidogrel treatment will be prospectively assessed.