Inclusion Criteria:
* Patients ≥ 65 years old
* Diagnosis of excessive supraventricular ectopy activity defined as ≥ 1% PAC / 24 h or any atrial runs ≥ 20 PACs on a 24-hour Holter ECG monitoring (the indication for the Holter will be let at the discretion of the doctor according to international guidelines indication)
* High risk embolism defined by a CHA2DS2VASC score ≥ 3
* Written consent from patient
* Patients able to attend consultations and Cerebral MRI at baseline and 24 months at the participating centre.
* Ability to understand and comply with the study protocol
* Affiliation of social security regime
Exclusion Criteria:
* According to the SmPC, any contraindication to Rivaroxaban (particularly patients with ongoing major bleeding, vascular complication, prior haemorrhagic stroke or over recent stroke) or one of its excipients.
* Inability to perform cerebral MRI
* Life expectancy \<24 months
* History of major hemorrhage after taking Rivaroxaban
* Documented atrial fibrillation or any other indication for oral anticoagulation
* Patients with previous documented AF
* Valvular congenital heart disease
* Anticoagulant agents in the month prior to the inclusion visit
* Acute coronary syndrome, coronary revascularization (percutaneous coronary intervention or coronary artery bypass surgery) or in the past 30 days
* Requires long-term antiplatelet therapy other than aspirin (i.e., patient requires any platelet aggregation inhibitor in addition to study treatment, in particular, the combination of two platelet aggregation inhibitors)
* Ongoing need for strong inhibitors of both CYP3A4 and P-glycoprotein (e.g., ketoconazole, itraconazole, ritonavir or clarithromycin)
* Ongoing need for strong inducers of both CYP3A4 and P-glycoprotein (e.g., rifampin, carbamazepine, phenytoin)
* Participants considered by the investigator to be unsuitable for the study for any of the following reasons:Patient refuse the treatment with rivaroxaban or anticipated to have poor compliance on study drug treatment or Unwilling to attend study follow-up visits
* Cancer or other life threatening conditions
* Severe, disabling stroke within the previous 6 months, or any stroke within the previous 14 days
* Conditions associated with an increased risk of bleeding:
1. Major surgery within the previous month
2. Planned surgery or intervention within the next 3 months
3. History of intracranial, intraocular, spinal, retroperitoneal or atraumatic intra-articular bleeding
4. Gastrointestinal hemorrhage within the past year
5. Symptomatic or endoscopically documented gastroduodenal ulcer disease in the previous 30 days
6. Hemorrhagic disorder or bleeding diathesis
7. Need for anticoagulant treatment of disorders other than atrial fibrillation
8. Fibrinolytic agents within 48 hours of study entry
9. Uncontrolled hypertension (systolic blood pressure greater than 180 mm Hg and/or diastolic blood pressure greater than 100 mm Hg)
10. Recent malignancy or radiation therapy (within 6 months) and not expected to survive 3 years
* Severe renal impairment (estimated creatinine clearance \<30 mL/min or less)
* Active infective endocarditis
* Active liver disease, including but not limited to, associated or not with coagulopathy and a clinically significant risk of bleeding, including cirrhotic patients with a Child Pugh class B or C score.
* Persistent ALT, AST, Alk Phos greater than twice the upper limit of the normal range
* Known active hepatitis C (positive HCV RNA)
* Known active hepatitis B (HBs antigen +, anti HBc IgM +)
* Known active hepatitis A
* Anemia (hemoglobin level less than 110 g/L) or thrombocytopenia (platelet count less than 150 X 109/L)
* Patients who have received an investigational drug in the past 30 days
* Patients considered unreliable by the investigator, or having any condition which, in the opinion of the investigator, would not allow safe participation in the study (e.g., drug addiction, alcohol abuse)
* Patient with cardiac prosthetic devices : Reveal, pace-maker, automatic implantable defibrillator
* Participation in another interventional clinical trial
* Patient on AME (state medical aid)
* Persons under psychiatric care
* Adults subject to a legal protection measure (guardianship, curatorship and safeguard of justice)Patients deprived of their liberty by a judicial or administrative decision
