Definitions and variables
The clinical tachycardia was defined as the tachycardia previously registered in a 12-lead ECG or, when 12-lead ECG was not available, the tachycardia registered in the ICD log in terms of cycle length and/or intracardiac electrogram morphology. Abnormal electrograms included late potentials registered during the patient’s baseline rhythm defined as a high frequency low amplitud signals occurring in the terminal part of the QRS complex (last 40 ms) or beyond QRS complex termination and diastolic or presystolic potentias registered during VT.
Complete activation mapping was considered when the critical isthmus and or exit of the tachycardia circuit could be clearly defined by entrainment maneuvers. Acute success was defined as non-inducibility of any type of sustained ventricular arrhythmias at the end of the procedure. Survival free of VT recurrence was defined as the absence of sustained VT, symptomatic or asymptomatic, either registered by intracardiac electrograms from an ICD or from a surface 12 lead ECG.
We also recorded the incidence of new-onset of hemodynamic inestability during the procedure or during the first 24-48 h after ablation and the possible relationship with VT induction and the use of activation mapping during the procedure. Hemodynamic inestability during the procedure was defined as persistent hypotension despite vasopressors and requiring mechanical support or procedure discontinuation. During the first 24-48h after the procedure any hemodynamic worsenig, the need of vasoactive drugs or ventricular assist device implantation was also cosidered as procedure-related hemodynamic decompensation.