What is the management of scar-related ventricular tachycardia (VT)?

Management of Scar-Related Ventricular Tachycardia

Catheter ablation is the definitive treatment for scar-related ventricular tachycardia (VT), with urgent ablation recommended for patients with incessant VT or electrical storm, and for those experiencing recurrent ICD shocks due to sustained VT. 1

Initial Assessment and Management

Hemodynamically Unstable VT

1. Immediate synchronized cardioversion (100-200 J monophasic) for unstable patients 1
2. Correct potentially causative or aggravating conditions:
   • Hypokalemia and other electrolyte abnormalities
   • Myocardial ischemia
   • Acid-base disturbances
   • Drug toxicity 2, 1

Hemodynamically Stable VT

1. Obtain 12-lead ECG to confirm diagnosis and morphology of VT 1
2. Antiarrhythmic medication:
   • First-line: IV amiodarone 300 mg over 10 minutes, followed by infusion of 1 mg/min for 6 hours, then 0.5 mg/min 1, 3
   • Alternative: IV procainamide 20-30 mg/min up to 12-17 mg/kg, followed by infusion of 1-4 mg/min (Class IIa recommendation) 2, 1
   • For VT associated with acute myocardial ischemia: IV lidocaine 50mg over 2 minutes, repeated every 5 minutes to a total dose of 200mg (Class IIb recommendation) 2, 1

Caution: Calcium channel blockers (verapamil, diltiazem) should not be used to terminate wide-QRS-complex tachycardia of unknown origin (Class III recommendation) 2, 1

Definitive Management: Catheter Ablation

Catheter ablation is the cornerstone of treatment for scar-related VT 1, 4. The procedure should be considered in the following scenarios:

1. Urgent ablation for:

   • Incessant VT
   • Electrical storm
   • Recurrent ICD shocks due to sustained VT 1

2. Pre-procedural assessment:

   • Cardiac MRI (gold standard for identifying scar tissue)
   • Echocardiography to assess structural abnormalities and LV function 1

3. Ablation strategies:

   • Scar dechanneling: Ablation at the entrance of conducting channels within scar tissue 5

     • This approach alone can render 54.5% of patients non-inducible
     • Requires fewer radiofrequency applications and shorter procedure time
     • Associated with better event-free survival at 2 years 5

   • Point-by-point ablation at exit site of reentry circuit 1

   • Linear lesion sets across identified isthmuses 1

   • Epicardial approach when:

     • Endocardial ablation fails
     • In patients with dilated cardiomyopathy or ARVC 1, 6

4. Mapping techniques:

   • Electroanatomical mapping to identify scar and conducting channels 4, 7
   • Activation and entrainment mapping during sustained VT (if hemodynamically tolerated) 4
   • Substrate-based mapping during sinus rhythm for hemodynamically unstable VT 4

Post-Ablation Management

1. Continuous cardiac monitoring for at least 24-48 hours 1

2. Antiarrhythmic therapy:

   • Maintenance antiarrhythmic therapy for 6-24 hours post-procedure
   • Consider chronic oral antiarrhythmic therapy with amiodarone, beta-blockers, or sotalol 1

3. ICD implantation/programming:

   • ICD implantation recommended for prevention of sudden cardiac death in patients with documented sustained VT
   • Catheter ablation reduces but may not eliminate the need for ICD therapy 1
   • Review ICD programming post-ablation 1

4. Long-term follow-up:

   • Initiate oral beta-blockers during hospital stay and continue thereafter in all patients without contraindications 1
   • Regular follow-up to monitor for VT recurrence

Outcomes and Prognosis

• Acute procedural success rates vary between studies:

  • Multicenter Thermocool: 49% acute success, 53% freedom from VT at 6 months
  • Euro-VT: 81% acute success, 51% freedom from VT at 6 months 1

• Scar dechanneling technique shows promising results:

  • Complete conducting channel elimination is associated with higher event-free survival
  • Patients requiring only scar dechanneling have better outcomes than those requiring additional ablation of residual inducible VT 5

• VT recurrence rates remain significant:

  • 24-26% at 1 year
  • 50-55% at 4 years 6

• Patients presenting with fast VT (cycle length ≤250 ms) are at higher risk for fast VT recurrence and may benefit most from ICD therapy 6

Potential Complications of Catheter Ablation

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

Catheter ablation combined with optimal medical therapy and ICD implantation when indicated represents the most comprehensive approach to managing scar-related VT and reducing associated morbidity and mortality.