Open, randomized, controlled, multicenter clinical investigation. Transesophageal echocardiography (TEE) for all patients within 14 days of the Enrolment Visit. Patients randomized to oral anticoagulation (OAC) will receive standard of care (SOC) vitamin K antagonist treatment throughout the 24 months clinical investigation period, managed by the primary care physician, with the goal of achieving and maintaining an INR of 2-3 (INR monitoring by the primary care physician every two weeks throughout study period).