The purpose of this study is to assess the safety and function of the Aegis Sierra Ligation System in accessing and closing off the left atrial appendage (LAA) using a minimally invasive epicardial access approach.

A minimum of 30 participants will be included in this study, which is being performed at a maximum of 8 centers in Canada and the United States. (A maximum of 15 participants at 4 US centers will be enrolled)

Participants will be considered for this treatment if their doctor(s) have determined they have documented non-valvular atrial fibrillation and are at increased risk for developing a stroke.

Study Purpose:

The objective of this early feasibility study is to assess the safety and function of the Aegis Sierra Ligation System (SLS) in ligating the left atrial appendage in patients with non-valvular atrial fibrillation and at risk for stroke. The results of this trial will be used to inform a larger pivotal trial that will allow for further health technology assessment and for Medical Device License applications.

General Design:

This is a prospective, single-arm, open-label, multi-center study. This study will screen patients with atrial fibrillation at risk for stroke. A minimum of 30 patients that meet all of the study's inclusion criteria, none of the exclusion criteria and consent to study participation will be enrolled. Patient accruement will take place at up to 8 North American centers (A maximum of 15 participants at 4 US centers will be enrolled).

Each subject will undergo the following study visits: Screening, LAA ligation Procedure (Day 0) and Post-procedure, Hospital Discharge, Day 7, Day 30, Day 90, Day 180 and Day 365.

The total duration of participation for subjects is anticipated to be 5 years post ligation procedure with the primary safety outcome assessed at the 30-day follow-up and the secondary endpoints assessed at Days 30, 180 and 365. Subjects will be also be contacted for an annual telephone follow-up evaluation from years 2 through 5 to assess for patient-reported long-term Major Adverse Events (MAE) and current health status.

Inclusion Criteria:

1. Age >=18 years
2. Documented non-valvular atrial fibrillation
3. Current CHA2DS2-VASc score of ≥2
4. Have an appropriate rationale to seek a non-pharmacologic alternative to oral anticoagulation (OAC) therapy
5. Willing and able to provide written informed consent
6. Willing and able to comply with study procedures and follow-up visits.
7. Able to take antiplatelet therapy post ligation procedure

Exclusion Criteria:

1. Cardiogenic shock or hemodynamic instability
2. Myocardial infarction in the past 3 months
3. Cerebral embolism, stroke, or TIA in past 3 months
4. Absence of a defined left atrial appendage on echocardiogram or CT scan
5. Previous cardiac surgery involving opening of the pericardium
6. History of pericarditis or pericardial tumor, a history of constrictive pericarditis or features which in the opinion of the investigator are suggestive of constrictive pericarditis
7. History of significant chest trauma of the anterior chest
8. Estimated life expectancy < 24 months
9. Chemotherapy in the past 12 months
10. Prior thoracic radiation therapy
11. Chronic liver disease (greater than Child-Pugh Class A), chronic renal disease/insufficiency/failure (creatinine >3.0 mg/dL and/or renal replacement therapy at the time of screening), or chronic end stage pulmonary disease (FEV1 less than 30% predicted).
12. Current use of long-term treatment with steroids. Does not include intermittent use of inhaled steroids for respiratory diseases.
13. Contraindication to transesophageal echocardiography (TEE).
14. Absolute contraindication to anticoagulation or antiplatelet therapy
15. Congenital Heart Disease or intracardiac/intrapulmonary shunts
16. Symptomatic or known significant carotid disease and/ or aortic arch atheroma
17. Known thrombus in the LAA/LA or thrombus visualized by TEE within 48 hours before procedure
18. Left ventricular ejection fraction (LVEF) below 30%
19. Pregnant, breastfeeding or planning pregnancy within next 12 months
20. Inappropriate appendage morphology (aberrant anatomy) as determined by imaging and assessed by Central Screening Committee
21. Current NYHA Class IV heart failure symptoms
22. Right ventricular dysfunction and /or pulmonary hypertension (>=50mmHG)
23. Moderate or greater valve disease (i.e., MVA <1.5cm2, AVA <1.5cm2), history of rheumatic mitral stenosis, or mechanical valve prosthesis.
24. Cardiac tumour
25. Known hypersensitivity to nickel
26. Patients in whom pericardial access will put the patient at risk (e.g. scoliosis, pectus excavatum, massive obesity with a BMI >40) as determined by clinical site Principal Investigator or Central Screening Committee.
27. Current enrollment in an investigation or study of a cardiovascular device or investigational drug that would interfere with this study.
28. Mental impairment or other conditions, which may not allow patient to understand the nature, significance and scope of the study.
29. Any other criteria, which would make the patient unsuitable to participate in this study as determined by clinical site Principal Investigator or Central Screening Committee (e.g., uncontrolled drug and/or alcohol addiction, extreme frailty).