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.