This study uses two AcQMap imaging and electroanatomical mapping systems (Acutus Medical) to simultaneously visualise and map patterns of wavefront propagation in both the left and right atria during atrial fibrillation in order to identify mechanisms of rhythm propagation and maintenance and the importance of the interaction of the left and right atria. Mapping will also be performed during pacing from different sites and cycle lengths to identify regions of abnormal conduction that may be related to the maintenance of atrial fibrillation.

Patients undergoing first time catheter ablation for atrial fibrillation with undergo simultaneous bi-atrial mapping using two linked AcQMap imaging and mapping systems from Acutus Medical. Mapping will be performed during AF, sinus rhythm and pacing (following cardioversion if required). Pacing will be undertaken from 3 sites in order to create different vectors of conduction and at varying cycle lengths and coupling intervals in order to identify regions of slow and anisotropic conduction. Patients will then undergo pulmonary vein isolation by radiofrequency ablation followed by ablation of non-pulmonary vein targets at the operators discretion (ablation in line with clinical practice and not as part of the study). Regions of focal firing, rotational or slow conduction during AF will be noted and the interaction between each atria described.

Inclusion Criteria:

• Participant is willing and able to give informed consent for participation in the trial.
• Male or Female, aged 18 years or above.
• Diagnosed with paroxysmal or persistent atrial fibrillation and planned for a catheter ablation procedure.
• In the Investigator's opinion is able and willing to comply with all trial requirements.

Exclusion Criteria:

• Physical or anatomical barriers to the use of two simultaneous mapping catheters
• Previous cardiac surgery
• Previous ablation (catheter or surgical)
• Female participant who is pregnant, lactating or planning pregnancy during the course of the trial.
• Any other significant disease or disorder which, in the opinion of the Investigator, may either put the participants at risk because of participation in the trial, or may influence the result of the trial, or the participant's ability to participate in the trial.
• Participants who have participated in another research trial involving an investigational medicinal product in the past 12 weeks. (Involvement in any other research trial is not a contraindication per se.)

Patients undergoing their first catheter ablation procedure for atrial fibrillation