• Composite endpoint of death, myocardial infarction, stroke, urgent coronary revascularization, stent thrombosis assessed at one year for the first hypothesis and between 6 up to 18 months of follow-up for the second hypothesis [ Time Frame: during the study (one year in both " monitoring " and " conventional " arms and during the periode from 6 up to 18 months in the "interruption" and "pursuit" arms) ] [ Designated as safety issue: No ]
  

• Stent thrombosis and urgent coronary revascularization [ Time Frame: 30 months ] [ Designated as safety issue: No ]
  
• Rate of individual event at one year follow-up in both " monitoring " and " conventional " arms but also during the period from one year up to 24 months in the " interruption " and " pursuit " arms. [ Time Frame: 30 months ] [ Designated as safety issue: No ]
  
• Time delay from treatment interruption (randomization 2) to any thrombotic event (stent thrombosis, urgent revascularization, acute myocardial infarction, cardiac death) treatment interruption(randomisation 2) [ Time Frame: 30 months ] [ Designated as safety issue: No ]
  
• Treatment compliance evaluated by the number of oral antiplatelet treatment in both arms and with respect to all individual events of the primary composite endpoint [ Time Frame: 30 months ] [ Designated as safety issue: No ]
  
• Rate of use of GP IIb/IIIa receptor antagonists in both " monitoring " and " conventional " arms before percutaneous coronary intervention and in bail out situations and in both. [ Time Frame: 30 months ] [ Designated as safety issue: No ]
  
• Rate of suboptimal responders as defined by ARU>550 for aspirin or by a % of inhibition <15% and or a PRU<235) and the average dosage of aspirin and clopidogrel (in mg) will evaluated before and after dose adjustment (J0) and after each dose adjustment [ Time Frame: 30 months ] [ Designated as safety issue: No ]
  
• Net clinical benefit (death, myocardial infarction, urgent revascularization, stent thrombosis, stroke, major bleeding) [ Time Frame: 30 months ] [ Designated as safety issue: No ]
  
• Medico-economic evaluations will be performed for both hypotheses. The rate of rehospitalisation and the length of stay will be used as economic indicators [ Time Frame: 30 months ] [ Designated as safety issue: No ]
  

Participating Centers : 30 french high PCI volume (>700) centers Rationale: Clopidogrel (75 mg/day), in combination with aspirin (75 mg/day), is currently the antiplatelet treatment of choice for prevention of stent thrombosis, and clinical trials have shown that, in high-risk patients, prolonged dual antiplatelet treatment is more effective than aspirin alone in preventing major cardiovascular events. However, despite the use of clopidogrel, a considerable number of patients continue to have cardiovascular events. Numerous in vitro studies have shown that individual responsiveness to clopidogrel but also to aspirin is not uniform in all patients and is subject to inter- and intraindividual variability. The recent possibility of bedside monitoring of oral antiplatelet therapy offers the unique opportunity of tailoring antiplatelet therapy. However, the relevance of such strategy has never been evaluated in a randomized prospective adequately powered study having long term follow-up (rationale 1). Late state stent thrombosis, especially in the era of drug eluting stent and after interruption of OAT, is another important safety issue raising the questions of the modalities of interruption of dual OAT after one year according to the most recent updated recommendations. Can we switch from dual to single OAT after one year? If so, what is the ischemic hazard? (Rational 2) Our first hypothesis is that a strategy of dose adjustment of OAT based on biological monitoring reduces the rate of the combined ischemic endpoints of death, urgent revascularization, stent thrombosis and stroke as compared to a conventional strategy (local practice without monitoring) in patients scheduled for DES implantation and followed up for one year. Our second hypothesis is that interruption of clopidogrel after one year of dual OAT is associated with a higher rate of the same combined ischemic endpoints as compared with patients in whom dual OAT is maintained during the subsequent 6 months of follow-up. Objectives: 1) To demonstrate the superiority of the strategy of monitoring with dose adjustment in suboptimal responders (Monitoring Arm) as compared to a more conventional strategy (Conventional Arm) with fixed dose regimen of both oral antiplatelet agents in all patients as defined by the international guidelines to reduce the primary endpoint evaluated one year after DES implantation. 2) to demonstrate the superiority of a strategy of pursuit of a dual OAT beyond one year (Pursuit Arm) as compared to a strategy of interruption (Interruption Arm).

Study duration (FPI-LPO) : 30 months Number of patients: 2500 patients. This number was obtained for the demonstration of the superiority of the strategy of monitoring (Monitoring Arm) over the conventional strategy (Conventional Arm) to reduce the primary endpoint by 33% (relative risk reduction).

Expected results: The ARCTIC study will provide answers to two major clinical challenges. It will also give a unique opportunity to assess the prevalence and the associated risk factors of suboptimal answers to OAT, but also to improve a suboptimal biological response. Finally, the economic impact of both strategies of monitoring and of interruption will be evaluated.