2 METHODS
The VTs per episode, recorded using an ICD or CRT-D device, were classified as regular or irregular VTs according to the RR interval variability of the cycle length. Based on this variability, we evaluated the rates of VT termination using ATP or shock therapy, and spontaneous termination, and acceleration. Additionally, the reproducibility of the RR interval variability of VTs (regular or irregular) in both an episode and an individual was evaluated.