• recurrence of any sustained clinical VT, stable or unstable, monomorphic or polymorphic, including VF, during the follow-up period [ Time Frame: 2 years ] [ Designated as safety issue: Yes ]
  

• Severe clinical events (death, number of syncopes, number of hospital admissions for a cardiac indication, number of episodes of electrical storm (more than 3 VT episodes in 24 hours)) during the follow-up period . [ Time Frame: 2 years ] [ Designated as safety issue: Yes ]
  
• Quality of life [ Time Frame: 2 years ] [ Designated as safety issue: No ]
  
• Number of adequate ICD interventions (shocks and overdrive episodes caused by recurrence of VT or VF and not supraventricular arrhythmias or mechanical lead problems). [ Time Frame: 2 years ] [ Designated as safety issue: Yes ]
  

The main objective of this study is to compare the time from randomization to the first recurrence of any VT in patients undergoing VT ablation (for stable VTs) and substrate ablation (for unstable VTs) after an initial episode of stable VT and patients not undergoing ablation, with both groups under the protection of an ICD.

Prior to the ablation, the patients will undergo electrophysiologic study (EPS) with programmed ventricular stimulation, with the aim to reproduce the clinical VT. Most patients with coronary artery disease, systolic LV dysfunction, and one episode of clinical sustained VT have more than one inducible VT at electrophysiologic study. Since any inducible VT can become a potential clinical VT (24), an attempt will be made to ablate the clinical stable VT, as well as all inducible morphologies, stable or unstable.

One of the following 2 ablation strategies will be possible for each VT:

• Substrate modification in sinus rhythm in case of unstable induced monomorphic VT which does not allow mapping and ablation in tachycardia, or noninducible stable clinical VT.
• VT ablation in tachycardia in case of stable VT

For each procedure the number of tachycardias , the type of each tachycardia (inducible or noninducible, stable or unstable), the ablation strategy for each tachycardia (it is possible that lesions deployed for one tachycardia will render another tachycardia noninducible as well) and the procedural outcome for each tachycardia will be documented.