 Intervention and control: The intervention group will be treated by LAAO, using the Amplatzer Amulet device. Implantation requires a catheterization procedure using venous access and transseptal puncture and is guided by angiography, fluoroscopy and transesophageal echocardiography TEE or intracardiac echocardiography ICE. Recommended post-implant antithrombotic therapy includes aspirin ASA therapy for at least 6 months, with or without clopidogrel for the first 45 days after implantation. The control group will receive medical therapy, delivered according to national standards and guidelines at the treating physicians discretion. This may include oral anticoagulation OAC vitamin-K antagonists, VKA, non-VKA OAC, antiplatelet therapy or no antithrombotic therapy at all. 