Chronic oral antithrombotic treatment is necessary in patients with mechanical heart valves and in the majority of patients with atrial fibrillation. When these patients have to undergo Percutaneous Coronary Intervention (PCI) with stenting, there is also an indication for treatment with aspirin and clopidogrel. However, triple therapy is known to augment the risk for bleeding complications.Unfortunately, no prospective data are available to solve this issue. Nevertheless, it all comes down to finding the ideal therapy in patients with both atrial fibrillation and percutaneous intervention to prevent thrombotic complications (e.g. stent thrombosis) without increasing the risk of bleeding. This prospective randomised study will assess the hypothesis that in patients on warfarin therapy and indication for elective percutaneous intervention, the combination warfarin & clopidogrel 75 mg/day is superior to triple therapy treatment in reducing the risk of bleeds while equally safe with respect to the prevention of thrombotic complications