Inclusion Criteria:

Candidates for this study must meet ALL of the following criteria:

* Age ≥ 18 years old
* First-time ablation procedure for AF
* Symptomatic AF which has been refractory to at least one antiarrhythmic medication (AAD). "Symptomatic" patients are those who have been aware of their AF anytime within the last 5 years. Symptoms may include, but are not restricted to, palpitations, shortness of breath, chest pain, fatigue, or other symptoms, or any combination of the above
* One of the following must apply:

* AF must either be PERSISTENT AF (non-US sites only) or HIGH BURDEN PAROXYSMAL AF - High burden paroxysmal AF is defined as episodes that terminate within 30 days and meet any ONE of the following criteria:
* More than 1 episode of AF per month in the preceding 6 months with at least 1 episode lasting >24 hours by symptoms,
* LA size of >/= 48 mm in the PLAX (parasternal long axis) view on echocardiography
* LA volume >/= 100 cc
* Total AF history >/= 10 years
* At least one episode of AF must have been documented by ECG, Holter, TTM, or telemetry strip within 24 months of inclusion in the study.
* Patients must be able and willing to provide written informed consent to participate in the study.
* Able and willing to comply with all pre-, post- and follow-up testing and requirements.

Exclusion Criteria:

Candidates will be excluded from the study if any of the following conditions apply:

* Patients with long-standing persistent AF >1 year for which cardioversion (pharmacologic or electrical) has failed or will never be attempted.
* Patients with AF felt to be secondary to an obvious reversible cause.
* Patients with contraindications to systemic anticoagulation with heparin or Coumadin.
* Patients who have previously undergone atrial fibrillation ablation.
* Patients who are pregnant (by history of menses or pregnancy test if history is considered unreliable.
* Left atrial size ≥55 mm (PLAX view on echocardiography).