Canadian Left Atrial Appendage Closure Study

Inclusion Criteria: * Subject has a documented history of paroxysmal, persistent or permanent non-valvular atrial fibrillation. * Subject is able to provide informed consent for the procedure. * Subject is able to be followed for the duration of the study. * Patient is able to take aspirin and Clopidogrel. Expected duration of dual antiplatelet therapy of 45 days. * Patient is not able to tolerate or adhere to the requirements of long term anticoagulation therapy. * Subject has a CHADS score \>/= 1. Exclusion Criteria: * The patient is known to have an extensive congenital cardiac anomaly which can only be adequately repaired by way of cardiac surgery. * The patient's size (i.e., too small for TEE probe, catheter size, etc.) or condition (active infection, etc.) would cause the patient to be a poor candidate for cardiac catheterization. * LAA anatomical exclusion (depth \<16mm and/or diameter \<11mm). * Patients with recent myocardial infarction, unstable angina, or decompensated congestive heart failure. (Recent is defined as within 180 days of implant date). * Patients with any type of serious infection less than one month prior to procedure. * Patient has demonstrated intracardiac thrombi on echocardiography (especially left atrial or left atrial appendage thrombi). * Patient is participating in another investigational drug or device study. * Subject has an implanted atrial septal defect (ASD) device or patent foramen ovale (PFO) device. * Subject had surgical ASD or PFO repair. * Subject has a moderate to severe aortic or mitral valve stenosis or regurgitation as assessed by the investigator. * Subject has a planned ablation procedure for atrial fibrillation within 60 days after the Ultrasept LAA closure device implant. * Subject has a New York Heart Association (NYHA) grade 4. * Patient has a left ventricular ejection fraction of 20% or less. * Patient has a life expectancy of less than one year. * Subject has had a recent major cardiac surgical procedure (recent is defined as within 180 days of implant date). * Subject is pregnant, breastfeeding, or desires to become pregnant during their first 180 days post-implant. * Subject has a medical disorder that would interfere with completion or evaluation of clinical study results (for e.g. uncontrolled hypertension, uncontrolled diabetes, renal failure, in situ inferior vena cava filter). * Patient has an allergy to Nickel.