Additional Study Information: The Amulet IDE trial is a prospective, randomized, multi-center active control worldwide trial, designed to evaluate the safety and effectiveness of the AMPLATZER Amulet Left Atrial Appendage Occluder. Subjects will be randomized in a 1:1 ratio between the Amulet LAA occlusion device (treatment) or a Boston Scientific WATCHMAN LAA closure device (Control). The trial will be conducted at up to 150 sites worldwide. All enrolled subjects will follow the protocol-required tests and assessments at each scheduled follow-up visit.