CellFX® Nanosecond Pulsed Field Ablation (nsPFA)™ Cardiac Surgery Clamp System to Treat Atrial Fibrillation

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 include the potential for surgical AF ablation, and completion of follow-up visits as specified in the clinical study protocol * Subject has history of documented paroxysmal atrial fibrillation (AF that is intermittent and terminates within ≤ 7 days of onset) or persistent/longstanding persistent atrial fibrillation (AF that is continuous and sustains for \> 7 days and requires intervention) within one year prior to enrollment. Documentation may include ECG, transtelephonic monitor (TTM), Holter monitor or telemetry strip from the study hospital or an outside physician * Subject is scheduled to undergo non-emergent cardiac surgical procedure(s) to be performed on cardiopulmonary bypass including open-heart surgery via sternotomy for one or more of the following: Mitral valve repair or replacement, Aortic valve repair or replacement, Ascending aortic aneurysms, Atrial Septal Defect (ASD)/Patent Foramen Ovale (PFO) 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 * Subject currently lives within a reasonable commuting distance of the investigational site and plans to remain geographically stable through 12 month follow up Exclusion Criteria: * Subject has an implantable electronic medical device. (i.e., pacemaker, implantable cardioverter-defibrillator (ICD), or Cardiac Resynchronization Therapy (CRT) or left atrial appendage (LAA) device * Subject has history or known to have LAA clot * Subject has a prosthetic heart valve * Stand- alone AF without indication(s) for concomitant Coronary Artery Bypass Graft (CABG) and/or valve surgery * Prior cardiac surgery including prior cardiac surgical ablation * Left Atrial diameter ≥ 6cm * Wolff-Parkinson-White syndrome or other Supra-Ventricular Arrhythmia, Atrioventricular (AV) nodal reentry * Documented history of persistent or long standing persistent atrial fibrillation longer than 10 years * Subjects requiring surgery other than CABG and/or cardiac valve surgery and/or atrial septal defect repair/PFO and ascending aorta * Prior history of medical procedure involving instrumentation of the left atrium (e.g., previous ablation) * Subjects that are on an AAD for ventricular arrhythmia. * STS Predicted Risk of Mortality (STS PROM) of 10 or higher * Class III or IV New York Heart Association (NYHA) heart failure symptoms * Prior history of stroke within 6 months * Documented ST-segment elevation Myocardial Infarction (MI) within the 6 weeks prior to study enrollment * Need for emergent cardiac surgery (per sit-to-stand (STS) test definition) * 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 (significant liver dysfunction with markedly significant elevation of liver enzymes, such as cirrhosis with decompensation, portal hypertension, or a history of hepatic failure) * A known drug and/or alcohol addiction * Mental impairment or other conditions that 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 * Subject has a contraindication to anticoagulation (e.g., a bleeding or clotting disorder such as Idiopathic Thrombocytopenic Purpura (ITP)) * Solid organ or hematologic transplant, or currently being evaluated for an organ transplant * Body mass index \> 45 kg/m2 * Any diagnosed connective tissue disorder * Severe Chronic Obstructive Pulmonary Disease (COPD) per sit-to-stand (STS) test definition * Use of any other investigational drug, therapy, or device within 30 days before enrollment or concurrent participation in another research study