3.1 Study groups
In a study group of 53 patients with an ICD or CRT-D, episodes with an unknown medication history (n = 77 in 7 patients), episodes with a cycle length < 240 ms (n = 8 in 7 patients), and episodes in which the starting point of ventricular tachyarrhythmia could not be confirmed on intracardiac electrocardiogram (n = 58 in 7 patients) were excluded; consequently, the remaining 465 episodes in 43 patients were included in the present analyses (Figure 3, Tables 1 and 2).