Unipolar and Bipolar Electrogram features
The average value of CL and CLSD was 155.7 ± 22.1 and 28.8 ± 7.9, respectively. Fig. 5A shows the distribution of CL and CLSD in the focal and non-focal activation points. At the points with focal activations, the minimum CL was 116 ms, and only 8 of 450 (1.7%) points had a shorter CL (≤ 120 ms) (defined as a CL of CFAE). There was no significant difference between the DFAs and the non-DFAs in CL (159.8 ± 21.5 ms vs. 159.7 ± 19.5 ms, p = 0.956). The CLSD was relatively shorter in the focal activation points than in the non-focal activation points, and 420 of 450 (93.3%) focal activation points had <30 ms. There was no significant difference between the DFAs and non-DFAs in the CLSD (20.5 ± 5.5 ms vs. 20.8 ± 6.3 ms, p = 0.620). The correlations between the focal intensity, CL, and CLSD are shown in Fig. 5B. There was a significant association between a decrease in CLSD and an increase in the number of repetitions of focal activation (CLSD estimates: -0.374; standard error: 0.037; p < 0.001). In contrast, no significant association was found between focal intensity and CL (CL estimates, -0.051; standard error, 0.031; p = 0.101).
The mean bipolar voltage at the points of focal activation was 0.73 ± 0.46 mV. One hundred fifty-one of 450 (33.6%) points were less than 0.5 mV, corresponding to LVA. The DFAs had a significantly lower amplitude than the non-DFAs (0.66 ± 0.41 mV vs. 0.81 ± 0.49 mV, p < 0.001, Fig. 6A). Regarding the bipolar electrogram morphologies, most focal activation points were categorized as the discrete type in 377 of 450 (83.8%) points, in which 241 of these 377 (63.9%) points consisted of single potential components. The combination type was observed in 71 of the 450 (15.8%) points. Only 2 of 450 (0.4%) points were classified as fractionated. There was no significant association between DFAs and non-DFAs in bipolar morphology (p = 0.176, Fig. 6B). Fig. 6C and 6D show examples of 3-dimensional maps representing the spatial relationship of the fractionated electrograms and focal activations. Most focal activations were located outside of the fractionated electrogram areas but were frequently observed adjacent to these areas.