Inclusion Criteria:
1. Male or non-pregnant female aged ≥18 years
2. Documented non-valvular AF (paroxysmal, persistent, or permanent)
3. High risk of stroke or systemic embolism, defined as CHA2DS2-VASc score of ≥ 2 for men and ≥ 3 for women
4. The patient is recommended for oral anticoagulation therapy (OAC), but has an appropriate rationale to seek a non-pharmacologic alternative to chronic oral anticoagulation
5. The patient deemed appropriate for LAA closure by the Site P.I. and a non-interventional physician using an evidenced-based decision-making tool on oral anticoagulants consistent with standard of care.
6. The patient is willing and able to comply with the protocol-specified medication regimen and follow-up evaluations
7. The patient (or legally authorized representative, (where allowed)) has been informed of the nature of the study, agrees to its provisions, and has provided written informed consent approved by the appropriate Institutional Review Board (IRB) or Ethics Committee (EC)
General Exclusion Criteria
1. Pregnant or nursing patients and those who plan pregnancy in the period up to 1 year following the index procedure. Female patients of childbearing potential must have a negative pregnancy test (per site standard test) within 7 days prior to index procedure.
2. Anatomic conditions that would prevent performance of an LAA occlusion procedure (e.g., prior atrial septal defect \[ASD\] or patient foramen ovale \[PFO\] surgical repair or implanted closure device, or obliterated or ligated left atrial appendage)
3. Atrial fibrillation that is defined by a single occurrence or that is transient or reversible (e.g., secondary thyroid disorders, acute alcohol intoxication, trauma, recent major surgical procedures)
4. Patients with a medical condition (other than atrial fibrillation) that mandates chronic oral anticoagulation (e.g., history of unprovoked deep vein thrombosis or pulmonary embolism, or mechanical heart valve)
5. History of bleeding diathesis or coagulopathy, or patients in whom antiplatelet and/or anticoagulant therapy is contraindicated
6. Active infection with bacteremia
7. Documented symptomatic carotid artery disease (\>50% diameter stenosis with prior ipsilateral stroke or TIA) or known asymptomatic carotid artery disease (diameter stenosis of \>70%)
8. Recent (within 30 days pre-procedure) or planned (within 60 days post-procedure) cardiac or non-cardiac interventional or surgical procedure
9. Recent (within 90 days pre-procedure) stroke or transient ischemic attack.
10. Recent (within 60 days pre-procedure) myocardial infarction
11. Vascular access precluding delivery of implant with catheter-based system
12. Severe heart failure (New York Heart Association Class III or IV)
13. Prior cardiac transplant, history of mitral valve replacement or transcatheter mitral valve intervention, or any mechanical valve implant
14. Renal insufficiency, defined as estimated glomerular filtration rate (eGFR) \<30 mL/min/1.73 m2 (by the Modification of Diet in Renal Disease equation), or dialysis at the time of screening
15. Platelet count \<75,000 cells/mm3 or \>700,000 cells/mm3, or white blood cell count \<3,000 cells/mm3
16. Patient has a known allergy, hypersensitivity or contraindication to aspirin, heparin, or device materials (e.g., nickel, titanium, gold) or that would preclude any P2Y12 inhibitor therapy, or the patient has contrast sensitivity that cannot be adequately pre-medicated
17. Current participation in another investigational drug or device study
18. Patient is a prisoner
19. Patient is unable to undergo general anesthesia
20. Known other medical illness or known history of substance abuse that may cause non-compliance with the protocol or protocol-specified medication regimen, confound the data interpretation, or is associated with a life expectancy of less than 2 years
21. Patient has a condition which precludes adequate transesophageal echocardiographic (TEE) assessment
Echocardiographic Exclusion Criteria
1. Left atrial appendage anatomy cannot accommodate the CLAAS device per manufacturer IFU
2. Intracardiac thrombus or dense spontaneous echo contrast, as visualized by TEE within 2 days prior to implant
3. Left ventricular ejection fraction (LVEF) \<30%
4. Circumferential pericardial effusion \>10 mm or symptomatic pericardial effusion, signs or symptoms of acute or chronic pericarditis, or evidence of tamponade physiology
5. Atrial septal defect that warrants closure
6. High risk patent foramen ovale (PFO), defined as an atrial septal aneurysm (exclusion \>15 mm or length \> 15 mm) or large shunt (early \[within 3 beats\] or substantial passage of bubbles)
7. Moderate or severe mitral valve stenosis (mitral valve area \<1.5 cm2)
8. Complex atheroma with mobile plaque of the aorta
9. Patient has evidence of cardiac tumor
