Inclusion Criteria:  Subject is greater than or equal to 18 years of age. Subject has documented history of atrial fibrillation. Subjects who received surgical ablation for their atrial fibrillation using CRYOF and on whom at least the following lesions were performed: Left and right pulmonary vein isolation, roof and floor lines, mitral annulus line and a connecting lesion from left atrial appendage to left pulmonary vein coronary sinus lesion and LAA exclusion , with a lesion duration of at least 2 minutes. Stable subject that underwent non-emergent cardiac surgical procedure(s) on cardiopulmonary bypass including open-heart surgery for one or more of the following: mitral valve repair or replacement, aortic valve repair or replacement, tricuspid valve repair or replacement, or coronary artery bypass procedures, or atrial septal defect (ASD) repair Left Ventricular Ejection Fraction ≥ 30% (determined by echocardiography or cardiac catheterization performed within 90 days of enrollment as documented in patient medical history). Subject is willing and able to provide written informed consent. Subject is willing and able to return for scheduled follow-up visits.  Exclusion Criteria:  Stand-alone AF without indication(s) for concomitant CABG and/or valve surgery. Previous left sided ablation procedures procedure. Untreated atrial flutter and symptomatic ventricular arrythmia Known carotid artery stenosis greater than 80% prior to index ablation procedure. Prior history of ischemic stroke or hemorrhagic stroke History of MI with ST elevation within 6 weeks prior to the index ablation Documented AF duration of greater than 10 years. Large left atrial size i.e., LA diameter >7 cm prior to the index ablation procedure. Subjects with active systemic infection prior to index ablation procedure. Subjects who had documented severe peripheral arterial occlusive disease defined as claudication with minimal exertion prior to the ablation procedure. Subjects with history of renal failure requiring dialysis or hepatic failure prior to the ablation procedure. 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. Subjects who are pregnant Subjects who had preoperative need for mechanical circulatory support or intravenous inotropes. Subjects who are on anti-arrhythmic drug therapy for the treatment of another arrhythmia. Subjects in currently undergoing chemotherapy. Subjects on long term treatment with oral or injected steroids (not including intermittent use of inhaled steroids for respiratory diseases). Subjects who had known connective tissue disorders at the time of index ablation procedure Subjects who had known hypertrophic obstructive cardiomyopathy at the time of index ablation procedure Subjects with known cold agglutinin. Subjects who had or tested positive for COVID-19 Subjects with bleeding disorders and/or inability to receive anticoagulation Subjects undergoing aortic dissection surgery as index procedure. Cardiac surgical re-intervention since the index cardiac surgery with concomitant AF ablation procedure