3.2 VT termination
Among the 465 episodes in 43 patients, 290 were managed with ATP therapy, 10 with shock therapy without ATP (shock therapy was administered after ATP therapy in 17), and 165 without therapy.
The characteristics of ATP therapy are summarized in Supplementary Table 2. The first pacing program for ATP therapy was set as burst pacing in all cases. ATP therapy terminated 85% of VT episodes (n = 246), and shock therapy terminated 100% of episodes (n = 27). After ATP delivery, the rate of spontaneous termination was 5% (n = 24), and the spontaneous termination rate without therapy was 31% (n = 145). VT termination could not be confirmed using intracardiac electrocardiography, i.e., episodes that were out of the VT zone without termination, in 5% of the episodes (n = 23).
In terms of ATP therapy, regular VTs showed significantly more successful terminations than irregular VTs (p < 0.001, odds ratio, 7.56). There was no significant difference in VT termination using ATP therapy between ischemic and non-ischemic cardiomyopathies. In addition, VT episodes with a faster rate showed a lower termination rate (p = 0.002, odds ratio, 0.97; Table 3). Spontaneous termination after ATP delivery occurred significantly more frequently in irregular than in regular VTs (p < 0.001, odds ratio, 30.58; Table 4). The VT rate had no significant effect on spontaneous termination after ATP delivery. For episodes in which no therapy was administered, spontaneous termination without therapy was more commonly observed in irregular than in regular VTs (p = 0.001, odds ratio, 6.06).