Voltage mapping
Following PV isolation, detailed voltage mapping was performed using a bipolar 3.5-mm tip catheter or multi-electrode mapping catheter during sinus rhythm or with pacing from the right atrium. Voltage mapping was not completed due to unstable cardiac rhythm in 8 of the total patients. (Figure 1) Mapping points were acquired to fill all color gaps on the voltage map using the electroanatomical mapping system. Respective fill and color interpolation thresholds were 15 mm and 23 mm using Carto 3 (Biosense Webster) and 20 mm and 7 mm using Ensite NavX (St. Jude Medical). Using Rhythmia (Boston Scientific), interpolation threshold was 5 mm.
Sites at which LVAs were recorded were then evaluated by high-density mapping to precisely delineate their extent, using the confidence module with the Carto 3 system and Ensite Automap with Ensite NavX. Adequate endocardial contact was confirmed by distance to the geometry surface and stable electrograms. Each acquired point was classified according to the peak-to-peak electrogram as follows: >0.5 mV, healthy; and <0.5 mV, LVAs, with the band pass filter set at 30 to 500 Hz. The target number of mapping points was ≥100 with the 3.5-mm tip catheter and ≥1000 with the multi-electrode mapping catheter throughout the left atrium. Patients were categorized by LVA size into 3 groups. Patients in Group A had none or small LVAs less than 5 cm2; those in Group B had mildly or moderately damaged LA which contained LVAs less than 20 cm2; and those in Group C had severely damaged LA which contained LVAs of more than 20 cm2 (Figure 2).