Electrophysiology and Mapping Procedure
Details of intracardiac access have been previously described.11 Antiarrhythmic drugs were discontinued at ≥ 5 half-lives before ablation. A 20-pole electrode catheter was placed in the high right atrium and coronary sinus vein. A 20-pole high-density mapping catheter (PentaRay, Biosense Webster, interelectrode spacing: 2-6-2 mm) were placed into the LA with the assistance of a steerable sheath (Agilis, St Jude Medical).
The surface electrocardiogram and intracardiac electrograms were recorded using a computer-based digital recording system (Claris, St Jude Medical). Intracardiac electrograms were filtered at 30 to 500 Hz and exported for offline analysis. All procedures were performed with a 3-dimentional mapping, CARTO®3 version 7 system (Biosense Webster Inc., Diamond Bar, CA, USA). After creating the LA geometry using fast anatomical mapping, the PentaRay catheter was positioned sequentially at the various sites of the LA to create a CARTFINDER map using 30-second unipolar signals in all electrodes with reference to Wilson’s Central Terminal filtered between 0.05 and 500 Hz. We did not attempt to map inside the pulmonary veins (PVs) and deep inside of the left atrial appendage (LAA) due to the potential difficulty in deploying the PentaRay catheter on the surface of those regions. Bipolar signals for each recording point were obtained simultaneously during CARTOFINDER mapping. The low voltage areas (LVA) were defined as the sites of bipolar voltage amplitude (< 0.5 mV) during AF.12 We also performed high-density bipolar electrogram mapping to identify the fractionated electrogram area using the interval confidence level mapping mode (ICL mode) on the CARTO system. The fractionated electrogram area was defined as ≥ 60% of the maximum value of the ICL.13