This study will investigate the effect of treatment with a high bolus dosage of Tirofiban (in addition to Aspirin, Heparin and 300mg or 600mg clopidogrel) on the rate of periprocedural myocardial infarction compared to Aspirin, Heparin (or bivalirudin) and 300mg or 600mg clopidogrel alone in patients resistant to aspirin and/or to clopidogrel.