This feasibility study will be conducted to demonstrate the initial safety and effectiveness of the CellFX® nsPFA™ Cardiac Clamp in performing a box lesion around the 4 pulmonary veins as an isolated procedure or as a part of a more extensive surgical ablation set in conjunction with concomitant cardiac surgical procedure.

This study is a prospective, multicenter, single arm, non-randomized, feasibility study. Adult subjects who are clinically indicated for a concomitant cardiac surgical procedure will undergo left pulmonary vein, roof and floor ablations to form a left atrial posterior box. All subjects will return to the hospital between 60-120 days post-surgical ablation procedure to undergo a cardiac electrophysiology study with electroanatomical mapping to assess electrical isolation of the pulmonary veins and left atrial posterior wall

Inclusion Criteria:

• Subject must be between 18 and 85 years of age
• Subject is willing and capable of providing Informed Consent to undergo study procedures which includes surgical AF ablation and completing follow-up visits as specified in the clinical study protocol
• Subject has history of documented atrial fibrillation within one year prior to enrollment. Documentation may include ECG, transtelephonic monitor (TTM), holter monitor or telemetry strip
• Subject is scheduled to undergo non-emergent cardiac surgical procedure(s) to be performed on cardiopulmonary bypass including open-heart surgery for one or more of the following: Mitral valve repair or replacement, Aortic valve repair or replacement, Ascending aortic aneurysms, or Coronary artery bypass procedures
• Left ventricular ejection fraction ≥ 30% (determined by echocardiography or cardiac catheterization performed within 60 days of enrollment as documented in patient medical history)
• Subject has a life expectancy of at least 5 years

Exclusion Criteria:

• Subject has an implantable electronic medical device. (i.e., pacemaker, ICD or CRT) or left atrial appendage device
• Subject has a prosthetic heart valve
• Stand-alone AF without indication(s) for concomitant Coronary Artery Bypass Graft (CABG) and/or valve surgery
• Previous surgical Maze procedure
• Prior cardiac surgery (Redo)
• Wolff-Parkinson-White syndrome or other Supra-Ventricular arrhythmia, Atrioventricular (AV) nodal reentry
• Subjects requiring surgery other than CABG and/or cardiac valve surgery and/or atrial septal defect repair.
• Prior history of medical procedure involving instrumentation of the left atrium (e.g., previous ablation)
• Class IV New York Heart Association (NYHA) heart failure symptoms
• Prior history of cerebrovascular accident or TIA within 6 months or at any time if there is residual neurological deficit
• Documented ST-segment elevation Myocardial Infarction (MI) within the 6 weeks prior to study enrollment
• Need for emergent cardiac surgery (i.e., cardiogenic shock)
• Known carotid artery stenosis greater than 80%
• Current diagnosis of active systemic infection
• Severe peripheral arterial occlusive disease defined as claudication with minimal exertion
• Renal failure requiring dialysis or hepatic failure
• A known drug and/or alcohol addiction
• Mental impairment or other conditions which may not allow the subject to understand the nature, significance and scope of the study
• Pregnancy or desire to get pregnant within 12-months of the study treatment
• Preoperative need for an intra-aortic balloon pump or intravenous inotropes
• Subjects who have been treated with thoracic radiation
• Subjects in current chemotherapy
• Subjects on long term treatment with oral or injected steroids (not including intermittent use of inhaled steroids for respiratory diseases)
• Subjects with known hypertrophic obstructive cardiomyopathy
• Subjects with known cold agglutinin
• History of abnormal bleeding and/or clotting disorder
• Contraindication to anticoagulation (i.e., Heparin, Dabigatran, Apixaban, Vitamin K Antagonists such as warfarin)
• Solid organ or hematologic transplant, or currently being evaluated for an organ transplant
• Body mass index > 40 kg/m2
• Use of any other investigational drug, therapy, or device within 30 days prior to enrollment or concurrent participation in another research study