Aortic Arch Related Cerebral Hazard Trial (ARCH)

Inclusion Criteria: Patients of both sexes aged ≥ 18 years with the following 4 inclusion criteria: * One of the 3 following ischemic events in the preceding 6 months: * Transient ischemic attack (TIA) * Non-disabling brain infarcts: * Inclusion within 6 months after onset * Duration of symptoms and signs greater than 24 hours * Neurological signs at the time of randomization with a Rankin Scale grade 3 or less * With normal computed tomography (CT) scan or CT scan showing a brain infarct (even hemorrhagic infarct) * Peripheral embolism * Atherosclerotic plaque in the thoracic aorta is defined as wall thickness ≥ 4 mm where the protruding material is the largest, measured at transesophageal echocardiography with multiplane transducer or a plaque less than 4 mm but with mobile component. * Informed consent signed * Life expectancy \> 3 years Exclusion Criteria: * Other causes of embolism: * Cardiac: endocarditis, atrial fibrillation, intra-cardiac thrombus, valvular prosthesis, rheumatic valvulopathy, left ventricular aneurysm, or ejection fraction less than 25% * Atherosclerotic stenosis ipsilateral to the embolic territory: internal carotid artery stenosis greater than 70%, or severe (judgment of the investigator) intracranial stenosis, or scheduled carotid endarterectomy (in that case inclusion is possible 30 days after the procedure) * Uncommon causes: dissection, vasculitis, procoagulant state, or sickle cell disease * Other exclusion criteria: * Intercurrent illness with life expectancy less than 36 months * Pregnancy and non-menopausal women * Unwillingness to participate * Poor medication compliance expected * Toxicomania * Absolute indication for anticoagulant therapy (e.g. atrial fibrillation, intracardiac thrombus, prosthetic valve) * Scheduled for carotid endarterectomy (randomization is possible 30 days after endarterectomy) * CT scan with an intracranial lesion other than brain infarction (space occupying mass, intracranial hemorrhage) * Transesophageal echocardiography (TEE) with plaque ≥ 4 mm in thickness distal to the supposed embolized artery (judgement of the investigator). * Contraindication to clopidogrel, aspirin, and oral anticoagulants