This study aims to assess whether a combined technique of substrate ablation and ablation of the clinically presenting VT at the site of early activation is superior to ablation of the clinically presenting VT alone, in enhancing long-term success of VT ablation.

Background: VT is found mostly in patients with structural heart disease. It is classified using morphological criteria (monomorphic or polymorphic), duration of arrhythmia (sustained or non-sustained) or the mechanism of arrhythmia formation (re-entry, increased automation or triggered activity). The therapeutic approach and prognostic estimates of these different types of VT depend to a great degree on the mechanistic basis of the disease as well as the extent of myocardial damage and success of the therapy is measured by the absence of recurrence.

Myocardial infarction with subsequent induction of VT is observed as a consequence of coronary artery disease (CAD). The infarct regions that are morphologically and electrically diseased can be arrhythmogenic and may form the substrate for macro-reentrant VT.

Although antiarrhythmic drugs remain the primary form of therapy for VT, non-pharmacologic techniques like implantable cardioverter-defibrillator (ICD) and catheter ablation (CA) are becoming increasingly popular because of advancement in technology as well as an increase in desire among patients to eliminate the arrhythmia with ablation rather than suppressing it with drugs. ICDs and CA effectively terminate VT on a short-term basis; but multiple morphologies, hemodynamic instability and non-inducibility limit the long-term success rate of CA. The 'substrate mapping' approach defines areas of ventricular scar which can be potential VT sources. Several studies on small groups of patients have shown that successful ablation of VT substrates either reduces the recurrence of VT to 19- 50% or reduces the frequency of recurrence as well as the requirement of anti-arrhythmic drugs (AADs).

Study design:

This study is a multicenter, randomized, open label, parallel-arm clinical trial. A total of 120 post-myocardial infarction patients will be randomized at a 1:1 ratio into 2 groups:

1. ablation targeting the clinically presenting VT at the site of early activation only, or
2. ablation targeting the clinically presenting VT at the site of early activation plus substrate-based RF ablation

Follow-up:

Patients will undergo ICD interrogation at 3, 6 and 12 months to collect VT episode data, VT symptom assessment, complication assessment and AAD records. Management of AADs will be at the discretion of the physician.

Inclusion Criteria:

• Previous Myocardial infarction
• Symptomatic, drug-refractory and haemodynamically stable VT following CAD
• Undergoing a VT ablation
• Implanted ICD

Exclusion Criteria:

• Documented valvular heart disease
• Acute myocardial infarction within the preceding 1 month
• Unstable angina
• Prolonged QT interval
• Patients with hemorrhagic or thrombophilic disorders
• Documented intra-atrial thrombus, tumor or other conditions which prevent easy catheter introduction