A stroke with with a symptom onset date within 30 days of an ablation procedure where at least one Phased RF ablation catheter was deployed into the left atrium considered related to the procedure and/or the investigational device by the independent clinical events committee

All subjects with a Phased RF ablation procedure who did not have a non-investigational catheter placed in the left atrium

For a participant, the 6-month effectiveness defined as meeting all of the following criteria: (1) acute procedural success, (2) greater than 90% reduction in atrial fibrillation/atrial flutter episodes lasting longer than 10 minutes as measured by 48-hour ambulatory ECG, (3) No amiodarone use for 90 days and no class I or class III antiarrhythmic drugs for at least 60 days prior to 6-month ambulatory ECG, and (4) free from direct current cardioversion for at least 60 days prior to the 6-month ambulatory ECG

Of the 129 subjects with an index Phased RF ablation procedure, 114 were evaluable for the 6-month efficacy objective. There were 15 subjects that were not included in the 6-month efficacy objective; 13 due to study exit prior to the 6-month visit and 2 due to no 6-month ambulatory ECG

Acute procedural success defined as: (1) Only Phased RF ablation catheters used in the left atrium, (2) all targeted pulmonary veins isolated, (3) all complex fractionated atrial electrograms and high frequency intracardiac electrogram amplitudes were mapped and ablated, and (4) sinus rhythm was restored at the end of the ablation procedure (with or without cardioversion)

All subjects who underwent a Phased RF study procedure

Greater than 70 percent reduction in the luminal diameter in any one or more of the pulmonary veins following a Phased RF ablation procedure

Number of subjects selected for participation in the pulmonary vein assessment cohort with baseline and 3-month evaluable magnetic resonance imaging scans of the pulmonary veins