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.
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.
