Stroke Feasibility Study

Inclusion Criteria: 1. Patient is ≥ 18 years and ≤ 80 years of age. 2. Patient has electrocardiographically confirmed non-valvular atrial fibrillation (paroxysmal, persistent, or longstanding persistent AF). 3. CHADS2 or CHA2DS2VASc score ≥2. 4. Patient has medical contraindication to long term anticoagulant therapy (OAC), defined as one or more of the following: * history of intracranial bleeding (e.g. due to amyloid angiopathy or other condition) which renders patient unsafe for OAC; * history of gastrointestinal, genitourinary, or respiratory tract bleeding due to permanent condition which renders patient unsafe for OAC; * HAS-BLED Score ≥ 3. 5. Patient is considered an acceptable surgical candidate, including use of general anesthesia. 6. Female patients must be of non-child bearing potential, or have a negative pregnancy test within 7 days prior to index procedure. Exclusion Criteria: 1. Stroke within 30 days, or TIA within 3 days, respectively, prior to index procedure. 2. Documented medical history of any penetrating trauma to thorax, or blunt trauma to thorax which resulted in a left pneumothorax or left hemothorax. 3. Myocardial infarction within 60 days prior to index procedure. 4. NYHA Class IV heart failure. 5. Ejection fraction \< 40% (based on baseline transthoracic echocardiography (TTE)). 6. Prior attempted obliteration of left atrial appendage (percutaneous or open cardiac surgery). 7. Previous catheter ablation with perforation or complication. 8. Prior open cardiac surgery, or percutaneous coronary intervention with associated unintended cardiac perforation, or pericardial adhesions are suspected. 9. History of pericarditis or pericardiocentesis. 10. Active infection, septicemia, or fever of unknown origin. 11. Concomitant elective surgical procedure (in addition to AtriClip placement) at the time of index procedure. 12. Planned atrial arrhythmia ablation procedure within six months following index procedure. 13. Underlying structural heart disease requiring planned surgical treatment within six months following the index procedure. 14. Cardiac or thoracic surgical procedure within the thirty days prior to index procedure. 15. Anticoagulation therapy for other medical condition (i.e. deep vein thrombosis) is required. 16. Patient unable to discontinue thienopyridines (e.g. clopidogrel) or non-ASA antiplatelet agents 4 days pre-operatively and abstain for at least 2 days post-operatively. 17. Renal Failure as defined by creatinine \> 2.0 mg/dl (\> 152.5 umol/L) and/or need for dialysis. 18. Known carotid artery diameter stenosis greater than 80%. 19. Patient has symptomatic or high-grade carotid disease (\>70% bilaterally). 20. Patient unable or unwilling to undergo transesophageal echocardiography (TEE). 21. Presence of thrombus in the left atrium or LAA, as determined by baseline TTE or Computed Tomography Angiogram (CTA). 22. Documented history of thrombophilic disorder, with diagnosis established via previous objective testing (e.g. familial screening for thrombophilia). 23. Moderate to Severe Chronic Obstructive Pulmonary Disease (FEV1 or VC\<70% predicted) or intolerant of single lung ventilation. 24. History of Hypercoagulopathy 25. Body Mass Index (BMI) \> 35. 26. Other medical illness or comorbidity that may cause non-compliance with the protocol, confound data interpretation (e.g. severe dementia), or limited life expectancy (i.e. \< 3 months). 27. Enrolled in another investigational device or drug study at the time of enrollment and during the course of the study. 28. Psychiatric disorder which in the judgment of the investigator could interfere with informed consent, completion of tests, therapy, or follow-up. 29. Patient is pregnant or intends to become pregnant within 6 months post-index procedure. Intraoperative Exclusion Criteria 1. Left atrial appendage width \< 29mm or \> 50mm, based on TEE imaging. 2. Presence of thrombus in the left atrium or LAA based on TEE imaging.