2.4 Mapping and ablation procedure
Transesophageal echocardiography was performed before the procedure in all patients to exclude any thrombus formation. The patients were studied under moderate to deep sedation while breathing spontaneously. Standard electrode catheters were placed in the right ventricular apex and coronary sinus after which a single transseptal puncture was performed. Unfractionated heparin was administered in a bolus form before the transseptal puncture to maintain an activated clotting time of more than 300 seconds. Mapping and ablation were performed using the NavX system (Abbott, Chicago, IL) as a guide after integration of a 3D model of the anatomy of the LA and PVs obtained from the MRI. A 20-pole circular mapping catheter (OptimaTM or Reflexion HDTM, Abbott) and ablation catheter-reconstructed LA posterior anatomy was aligned with the MRI.8Subsequently, a phase mapping using the ExTRa Mapping and complex fractionated atrial electrogram (CFAE) mapping using the NavX system were performed simultaneously. As for the CFAE mapping, a definition of the excitation cycle length of below 120 ms was employed.9