Comparison of Two Strategies for Catheter Ablation of Atrial Fibrillation - a comparison of ablation guided by Cartomerge and NavX Fusion. 3D mapping systems are widely used in catheter ablation of AF. Integration of a previously acquired image of the left atrium into the electroanatomical (EA) map offers several potential advantages, including visualisation of the complex anatomy of the left atrium, reduction of fluoroscopy time and improved results . The two most widely used systems are Cartomerge (Biosense Webster, etc) and NavX Fusion (SJM, etc). Although both systems have been independently validated, their clinical utility has not previously been directly compared in a randomised trial

Patients are randomised to either NavX Fusion or Cartomerge. They undergo a standard catheter ablation procedure and data is collected. Both systems are routinely used in our clinical practise. This is a comparison trial of 2 mapping technologies.

Inclusion Criteria:

• Be at least 18 years of age
• Be undergoing their first planned procedure for electrophysiology mapping and ablation in the left atrium of AF
• Be willing and able to sign the study specific informed consent
• Have a negative pregnancy test for female subjects of child bearing potential

Exclusion Criteria:

• Have a left ventricular ejection fraction (LVEF) of <40% as evaluated by pre-procedure TTE
• Have any contraindication or allergy to routine procedural medications or catheter materials
• Have any condition for which the investigator feels it is unsafe for the subject to undergo an invasive electrophysiology procedure (EP) catheterisation
• Be currently participating in another clinical research study
• Have any condition for which the subject's life expectancy is less than twelve months