The purpose of this study is to assess the safety and effectiveness of the Circular and Crescent Mapping and Ablation catheters and the workflow of the Multi-Electrode Irrigated Pulmonary Vein Isolation System when used for the treatment of drug refractory symptomatic paroxysmal atrial fibrillation (PAF).

The study will include a Workflow Phase to verify consistent workflow of all study device components and evaluate acute safety. Upon meeting the defined criteria, the Workflow Phase will be closed and further enrollment will be toward the Main Study Phase which includes the roll-in (the first 3 subjects enrolled at each site following the closure of the Workflow Phase) and Subpopulation Neurological Assessments (SNA) substudy subjects. SNA assessment is a prospective, non-randomized, controlled, acute assessment of two ablation devices to determine if intracerebral microemboli are generated during or immediately after radiofrequency ablation therapy for PAF. SNA subjects will remain and complete the Main Study Phase. However, SNA-control subjects will not be considered part of the Main Study Phase. All subjects, including the subjects enrolled under the Workflow Phase will be included in the Safety Cohort (evaluated for Primary Safety endpoint and all Secondary Safety endpoints).

Inclusion Criteria:

1. Patients with symptomatic Paroxysmal Atrial Fibrillation (PAF) who have had at least one documented Atrial Fibrillation (AF) episode in the twelve (12) months prior to enrollment. Documentation may include electrocardiogram (ECG), transtelephonic monitor (TTM), Holter Monitor (HM), or telemetry strip.
2. Failure of at least one antiarrhythmic drug for AF (class I or III, or Atrioventricular (AV) nodal blocking agents such as beta blockers and calcium channel blockers), as evidenced by recurrent symptomatic AF, or intolerable side effects.
3. Age 18 years or older.
4. Able and willing to comply with all pre-, post- and follow-up testing and requirements.
5. Signed Patient Informed Consent Form.

Exclusion Criteria:

1. AF secondary to electrolyte imbalance, thyroid disease, or reversible or non-cardiac cause.
2. Patients with Persistent or Long-standing AF (AF episode lasting > 30 days in duration.
3. Diagnosed atrial myxoma.
4. Left atrial size > 5.5cm.
5. Left Ventricular ejection fraction < 40%.
6. Contraindication to Computed Axial Tomography/Magnetic Resonance Imaging (CT/MRI) procedures
7. New York Heart Association Class III or IV.
8. Previous ablation for enrolled arrhythmia (AF).
9. Documented left atrial thrombus on imaging (example: transesophageal echocardiography or intracardiac echocardiography).
10. Myocardial Infarction within the previous 60 days (2 months).
11. Any valvular cardiac surgical procedure (that is, valve repair or replacement and presence of a prosthetic valve).
12. Coronary artery bypass graft procedure with the last 180 days 6 months.
13. Cardiac Surgery (that is, ventriculotomy, atriotomy) within the past 60 days (2 months).
14. Awaiting cardiac transplantation or other cardiac surgery within the next 365 days (12 months).
15. History of documented thromboembolic event within the past one (1) year.
16. Significant pulmonary disease, (example: restrictive pulmonary disease, constrictive or chronic obstructive pulmonary disease) or any other disease or malfunctions of the lungs or respiratory system that produces chronic symptoms.
17. Significant congenital anomaly or medical problem that in the opinion of the investigator would preclude enrollment in this study.
18. Active illness or active systemic infection or sepsis.
19. Unstable angina.
20. History of blood clotting or bleeding abnormalities.
21. Contraindication to anticoagulation (that is, Heparin or Warfarin).
22. Life expectancy less than 365 days (12 months)
23. Presence of intramural thrombus, tumor or other abnormality that precludes catheter introduction or manipulation.
24. Women who are pregnant (as evidence by pregnancy test if subject is of child bearing potential) and/or breast feeding.
25. Presence of a condition that precludes vascular access.
26. Enrollment in an investigational study evaluating another device or drug.

Safety population (cohort): For the main study, this population includes enrolled subjects who underwent insertion of study catheters. For the NAVISTAR® THERMOCOOL® arm, this population includes enrolled subjects, but excludes two subjects (1 with low pre-ablation international normalized ratio (INR) and 1 missing post procedure neurological exam).

12 Months post study procedure

"Serious Adverse Events"/"Other (Not Including Serious) Adverse Events" tables: for the "NAVISTAR® THERMOCOOL® (SNA Subpopulation Only)" arm the "at Risk #" represents subjects enrolled and treated, including the 1 subject excluded from the SNA analysis due to missing neurological exams. (Excluding the subject not treated).