The purpose of this study is to assess the safety and performance of the Hansen Medical Sensei Robotic System and Artisan Catheter when used to robotically manipulate RF ablation catheters for the treatment of paroxysmal atrial fibrillation (irregular heartbeats originating in the upper chambers of the heart).

Subjects who satisfy the inclusion and exclusion criteria will be treated with an RF ablation catheter and Artisan guide catheters controlled by the Sensei X Robotic Catheter System.

Subject will be followed for a period of one year post ablation procedure.

Follow up visit time frames will be conducted at 7-day, 30-day, 90-day, 180-day and 365-day.

Inclusion Criteria:

1. Subjects with paroxysmal atrial fibrillation who have had two or more spontaneously terminating episodes of atrial fibrillation, that last longer than 30 seconds and shorter than 7 days, in the nine months prior to enrollment. At least one episode must be documented with EKG, TTM, Holter monitor, or telemetry.
2. Failure of at least one Class I - IV anti-arrhythmic drug (AAD) for PAF as evidenced by recurrent symptomatic PAF, or intolerable side effects due to AADs. AADs are defined in Appendix B.
3. Signed informed consent.
4. Age 18 years or older
5. Able and willing to comply with all pre-, post-, and follow-up testing and requirements.

Exclusion Criteria:

1. Atrial fibrillation secondary to electrolyte imbalance, thyroid disease, or reversible or non-cardiac cause.
2. Previous ablation for atrial fibrillation.
3. Atrial fibrillation episodes that last less than 7 days and are terminated by cardioversion.
4. Previous valvular cardiac surgery procedure.
5. Cardiac artery bypass graft procedure within the previous 180 days.
6. Previous septal defect repair.
7. Expecting cardiac transplantation or other cardiac surgery within the next 180 days.
8. Coronary PTCA/stenting within the previous 180 days.
9. Documented left atrial thrombus on ultrasound imaging (TEE).
10. Documented history of a thrombo-embolic event within the previous 365 days.
11. Diagnosed atrial myxoma.
12. Presence of an implanted ICD.
13. Presence of permanent pacing leads.
14. Significant restrictive, constrictive, or chronic obstructive pulmonary disease or any other disease or malfunction of the lungs or respiratory system with chronic symptoms.
15. Significant congenital anomaly or medical problem that in the opinion of the investigator would preclude enrollment in this study.
16. Women who are pregnant.
17. Acute illness or active infection at time of index procedure documented by either pain, fever, drainage, positive culture and/or leukocytosis (WBC > 11,000 mm3) for which antibiotics have been or will be prescribed.
18. Creatinine > 2.5 mg/dl (or > 221 µmol/L).
19. Unstable angina.
20. Myocardial infarction within the previous 60 days.
21. Left ventricular ejection fraction less than 40%
22. History of blood clotting or bleeding abnormalities.
23. Contraindication to anticoagulation medications.
24. Contraindication to computed tomography or magnetic resonance imaging procedures.
25. Life expectancy less than 1 year.
26. Enrollment in another investigational study.
27. Uncontrolled heart failure (NYHA class III or IV heart failure).
28. Presence of an intramural thrombus, tumor, or other abnormality that precludes catheter introduction or positioning.
29. Presence of a condition that precludes vascular access.
30. Left atrial size ≥ 50mm.
31. INR greater than 3.0 within 24 hours of procedure.