The purpose of this study is to demonstrate that the Estech COBRA Surgical System is an effective treatment for patients with irregular heart beats who are undergoing heart surgery.

The objective of the trial is to demonstrate that the creation of epicardial and endocardial lesions with temperature-controlled radiofrequency (TCRF) ablation applied using the Estech COBRA® Surgical System during concomitant heart surgery is a safe and effective treatment for non-paroxysmal atrial fibrillation (AF).

Inclusion Criteria:

All subjects are required to meet the following inclusion criteria in order to be considered eligible for participation in this trial:

1. Subject is scheduled to undergo elective on-pump cardiac surgical procedure(s) for one or more of the following:

   1. Mitral valve repair or replacement,
   2. Aortic valve repair or replacement,
   3. Tricuspid valve repair or replacement, or
   4. Coronary Artery Bypass procedures;

2. Subject has history of a non-paroxysmal form of AF for greater than 3 months and has failed at least one attempt at electrical cardioversion or had a successful attempt at electrical cardioversion but had a recurrence of AF within 30 days of the cardioversion;

3. Age 18 to 80 years old;

4. Left ventricular ejection fraction (LVEF) ≥ 30%;

5. Subject has no contraindications to intraoperative transesophageal echocardiography;

6. Subject has a life expectancy greater than 12 months; and

7. Willing and capable of providing Informed Consent to undergo surgery and participate in all examinations and follow-ups associated with this clinical trial.

A subject is considered to have failed electrical cardioversion if they did not achieve sinus rhythm for at least 30 seconds following the attempted cardioversion.

Exclusion Criteria:

Subjects will be excluded from participating in this trial if they meet any of the following exclusion criteria:

1. History of non-paroxysmal AF less than 3 months or for more than 5 years;
2. History of prior cardiac ablative surgical or catheter-based therapy;
3. Previous cardiac surgery (redo) or other intrapericardial procedures;
4. Class IV NYHA heart failure;
5. Known carotid artery stenosis greater than 80% or previous carotid endarterectomy;
6. Wolff-Parkinson-White syndrome;
7. Need for emergent cardiac surgery (e.g., cardiogenic shock);
8. Untreated hyperthyroidism;
9. Untreated hypothyroidism;
10. Acute pulmonary disease;
11. Electrolyte imbalance;
12. History of myocarditis;
13. Presence of a previously implanted device in or adjacent to the treatment target area that may alter the delivery of therapy (e.g., valvular prosthesis or ring, pacemaker with leads in coronary sinus or internal defibrillator leads);
14. History of pericarditis;
15. Previous left phrenic nerve paralysis;
16. Bullous lung disease;
17. Presence of active endocarditis, or local or systemic infection;
18. Recent myocardial infarction (< 3 months);
19. Renal failure requiring dialysis or hepatic failure or creatinine of >2 mg/dL preoperatively;
20. Antiarrhythmic drug therapy required for the treatment of a ventricular arrhythmia;
21. Preoperative need for an intra-aortic balloon pump or intravenous inotropes;
22. Severe peripheral arterial occlusive disease defined as claudication with minimal exertion;
23. Therapy resulting in compromised tissue integrity including: thoracic radiation, chemotherapy, long term treatment with oral or injected steroids, or known connective tissue disorders;
24. Documented left atrial size of 6 cm or more;
25. History of cerebrovascular disease or accident, including stroke or transient ischemic attack (TIA) within 6 months prior to enrollment;
26. Known contraindication to anticoagulant therapy or inability to comply with anticoagulant therapy;
27. Pregnancy, planned pregnancy (females of childbearing potential must have a negative pregnancy test prior to enrollment and agree not to become pregnant during the trial) or breastfeeding;
28. Forced expiratory volume in 1 second less than 30% of predicted value or need for home oxygen therapy; or
29. Surgical management of hypertrophic obstructive cardiomyopathy.