When is catheter ablation for ventricular tachycardia (VT) recommended?

Catheter Ablation for Ventricular Tachycardia: Indications and Recommendations

Urgent catheter ablation in specialized or experienced centers is strongly recommended for patients presenting with incessant VT or electrical storm resulting in ICD shocks. 1

Primary Indications for Catheter Ablation in VT

Catheter ablation is indicated in the following scenarios:

1. Urgent/Emergency Situations:

   • Incessant VT or electrical storm resulting in ICD shocks 1
   • Patients with hemodynamically unstable VT who are refractory to medications 1, 2

2. Recurrent VT with ICD:

   • Patients with recurrent ICD shocks due to sustained VT 1
   • After first episode of sustained VT in patients with ischemic heart disease and an ICD (Class IIa recommendation) 1

3. Specific VT Types:

   • Bundle-branch reentrant VT (Class I recommendation) 1
   • Symptomatic outflow tract VT when medications are ineffective/not tolerated 1
   • Symptomatic VA arising from papillary muscles when medications fail 1
   • Verapamil-sensitive idiopathic LV tachycardia related to interfascicular reentry 1
   • Recurrent episodes of idiopathic VF initiated by PVCs with consistent QRS morphology 1
   • PVC-induced cardiomyopathy (generally >15% of beats) 1

Approach to VT Management

Step 1: Initial Stabilization

• For hemodynamically unstable VT: Immediate synchronized cardioversion 2
• For stable VT: Consider antiarrhythmic medications first (lidocaine, amiodarone, or procainamide) 2

Step 2: Determine Underlying Substrate

• Ischemic heart disease (post-MI scar)
• Non-ischemic cardiomyopathy
• Structurally normal heart (idiopathic VT)

Step 3: Risk Stratification

• Patients with post-MI scar have better outcomes with catheter ablation compared to non-ischemic cardiomyopathy 1
• Consider ICD implantation in eligible patients undergoing catheter ablation 1

Evidence for Catheter Ablation Efficacy

Ischemic Cardiomyopathy

• The VANISH trial showed catheter ablation resulted in 28% relative risk reduction in death, VT storm, and appropriate ICD shock compared to escalated drug therapy 3
• Particularly effective in patients having VT despite amiodarone therapy 3
• Success rates from multiple studies:
  • Multicenter Thermocool study: 49% acute success, 53% freedom from VT at 6 months 1
  • Cooled RF Multi Center study: 41% acute success, 46% freedom from recurrent VA 1
  • Euro-VT study: 81% acute success, 51% freedom from recurrent VT 1
  • SMASH-VT: Significant reduction in VT episodes (33% to 12%) and ICD shocks (31% to 9%) 1

Timing of Ablation

• The BERLIN VT trial compared preventive VT ablation (before ICD implantation) versus deferred ablation (after 3 ICD shocks) and found no significant difference in mortality or hospitalization, though there were numerical reductions in sustained ventricular arrhythmias (39.7% vs 48.2%) and appropriate ICD therapy (34.2% vs 47.0%) in the preventive group 4

Technical Considerations

Mapping Approaches

• Activation mapping during ongoing VT (when hemodynamically tolerated) 1
• Substrate ablation in sinus rhythm (for hemodynamically unstable VT) 1
• Three-dimensional electro-anatomical mapping systems to localize abnormal ventricular tissue 1
• Non-contact mapping for hemodynamically unstable VT 1

Ablation Strategies

• Point-by-point ablation at exit site of re-entry circuit (scar dechanneling) 1
• Linear lesion sets 1
• Ablation of local abnormal ventricular activity (scar homogenization) 1
• Epicardial mapping and ablation may be required, particularly in DCM or ARVC 1

Important Caveats and Limitations

1. Procedural Risks:

   • Damage to coronary vasculature during epicardial ablation
   • Inadvertent puncture of surrounding organs
   • Left phrenic nerve palsy
   • Pericardial tamponade 1

2. Efficacy Limitations:

   • VT recurrence is common, making ablation often palliative rather than definitive 5
   • Many patients continue to require antiarrhythmic therapy post-ablation 5
   • Multiple reentrant circuits may coexist, making ablation of a single VT insufficient 6
   • Critical VT zones may be epicardial or intramural, not just subendocardial 6

3. Patient Selection:

   • Hemodynamic tolerance of VT is necessary for certain mapping approaches 6
   • Infarct regions can be large, making mapping challenging 6

Conclusion

Catheter ablation is an effective treatment for VT, particularly in patients with ischemic heart disease who have recurrent VT episodes despite antiarrhythmic medications. It should be considered early in patients with electrical storm or incessant VT. While it significantly reduces VT burden, it should be viewed as complementary to ICD therapy rather than a replacement in patients with structural heart disease.