LVA mapping and analysis
Two different voltage maps were created using the 2 HDG bipolar configurations (along the spline and HD wave solution). There was a significant difference in the LVAs/LA surface between that using the HD wave solution and that along the spline (3.9±11% vs. 7.3±14%, P<0.001) (Figure 2 ). The extent of the LVZ was calculated as the percentage of the LA surface area and was categorized into stages 1 (minimum LVA, <5%), 2 (mild, ≥5% to <20%), 3 (moderate, ≥20% to <30%), and 4 (extensive, ≥30%). Sixty-eight of 73 (93.2%) patients with AF had minimum to mild LVAs (<10%) using the HDG with the HD wave solution regardless of an enlarged LAD and LA volume.
As shown in Figure 1B, LVAs were found in 194 (23.2%) sites out of 835. LVAs were frequently identified in the septal, anterior, and posterior regions of the LA. There was a significant difference in the LVA (<0.5mV)/LA surface area between the patients with and without recurrent AF/AT (6.4±8.0% vs. 2.5±2.6% P=0.003) as shown in Table 3. In addition, though there was no significant difference in the number of %NPs≧50% that overlapped with LVAs between the two groups (0.9±1.1 vs. 0.6±1.0, P=0.178), there were a significant difference in the number of high-DF sites ≧7Hz that overlapped with LVAs between the two groups (0.5±0.8 vs. 0.2±0.7, P=0.026). Further, high-DF sites ≧7Hz overlapping with LVAs were frequently identified in the septal, roof, and inferior regions of the LA and the %NPs≧50% overlapping with LVAs in the anterior and septal regions (Figure 1C ). Furthermore, the number of sites that overlapped with all regions (LVAs, high-DF sites ≧7Hz and %NPs≧50%) included only 6 (0.7%) out of 835 sites (1 anterior, 2 posterior, 1 septal, 1 roof, and 1 LAA). A representative case is shown in Figure 3 .