Aortic Arch Related Cerebral Hazard Trial (ARCH) (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