Inclusion Criteria:  Patients aged ≥ 70 years A diagnosis of ischemic stroke or TIA within 14 days from inclusion.  Exclusion Criteria:  Previously diagnosed atrial fibrillation Contraindication to oral anticoagulant treatment according to Summary of Product Characteristics. Indication for anticoagulant treatment other than atrial fibrillation, e.g. venous thromboembolism or mechanical heart valve prosthesis Dual antiplatelet therapy not interchangeable to oral anticoagulation Patients with pacemaker, implantable cardioverter defibrillator or implantable cardiac monitor. Patients who, according to the investigator, will not be able to comply with the study protocol.