2.6. VT burden
The pre-procedure VT burden was defined as the number of VT episodes and shock therapies up to 2 years from the time of the ablation procedure. The post-procedure VT burden was determined after 2 years from the day of ablation procedure. In redo procedures, the pre-procedure VT burden was defined as the number of VT episodes occurring between the previous ablation procedure and the when the redo ablation procedure was performed. VT episodes were defined as continuous VT for 30 seconds and/or a syncopal events, or as VT that required an appropriate intervention for termination. We also defined incessant VT that persisted or immediately reoccurred despite appropriate intervention to terminate the VT.