What is the management approach for Scar-related Ventricular Tachycardia (SCAR 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

Diagnosis and Assessment

• Cardiac Imaging:

  • Cardiac MRI is the gold standard for identifying scar tissue and guiding ablation procedures 2
  • Echocardiography to assess structural abnormalities and LV function 2

• 12-lead ECG during tachycardia to document VT morphology:

  • Scar-related VT is typically monomorphic with QRS morphology determined by exit site of reentry circuit 1
  • Helps in mapping and planning ablation procedures 2

• Electrophysiologic study to confirm diagnosis, map reentry circuits, and guide ablation strategy 2

Acute Management

1. Hemodynamically unstable VT:

   • Immediate electrical cardioversion/defibrillation 2

2. Hemodynamically stable VT:

   • Antiarrhythmic medications:
     • Amiodarone: 150 mg IV over 10 minutes, followed by infusion of 1 mg/min for 6 hours, then 0.5 mg/min for 18 hours 2
     • Lidocaine: 50mg IV over 2 minutes, repeated every 5 minutes to total dose of 200mg 2
     • Procainamide: 20-30 mg/min up to 12-17 mg/kg, followed by infusion of 1-4 mg/min 2

3. Beta-blockers should be administered during hospital stay and continued thereafter in all patients without contraindications 2

Definitive Management: Catheter Ablation

Indications for Catheter Ablation (Class I recommendations):

• Urgent catheter ablation for incessant VT or electrical storm 1
• Recurrent ICD shocks due to sustained VT 1
• Bundle-branch reentrant VT 1
• After first episode of sustained VT in patients with ischemic heart disease and an ICD (Class IIa) 1

Ablation Techniques:

1. Mapping Approaches:

   • Activation mapping during ongoing VT (when hemodynamically tolerated) 1
   • Substrate ablation in sinus rhythm (for unstable VT) using 3D electro-anatomical mapping 1
   • Non-contact mapping for hemodynamically unstable VT 1

2. Ablation Strategies:

   • Point-by-point ablation at exit site of reentry circuit (scar dechanneling) 1, 3
   • Linear lesion sets across identified isthmuses 1
   • Scar homogenization (complete substrate modification) 4
   • Core isolation (targeting arrhythmogenic "cores" within scar) 4

3. Epicardial Approach:

   • Required more often in patients with dilated cardiomyopathy or ARVC 1
   • Useful when endocardial ablation fails (Class IIa) 1

Outcomes of Catheter Ablation:

• Acute success rates: 41% to 81% 2
• Freedom from VT at 6 months: 46% to 53% 2
• Better outcomes in post-MI scar compared to non-ischemic cardiomyopathy 2
• Scar dechanneling alone results in low recurrence and mortality rates in more than half of patients 3

Potential Complications:

• Damage to coronary vasculature
• Inadvertent puncture of surrounding organs
• Left phrenic nerve palsy
• Pericardial tamponade 1
• In bundle branch ablation, severely impaired atrioventricular conduction requiring permanent pacing 1

Long-term Management

1. ICD Implantation:

   • Recommended for prevention of sudden cardiac death in patients with documented sustained VT 2
   • Catheter ablation reduces but may not eliminate the need for ICD therapy 1

2. Pharmacological Therapy:

   • Beta-blockers as first-line therapy 2
   • Amiodarone may be considered for symptom relief but has no effect on mortality 1
   • Sotalol as an alternative for patients who cannot tolerate amiodarone 2
   • Sodium channel blockers (class IC) are not recommended for patients with coronary artery disease 1

3. Post-ablation Care:

   • Continuous cardiac monitoring for at least 24-48 hours 2
   • Maintenance antiarrhythmic therapy for 6-24 hours post-procedure 2
   • Consider chronic oral antiarrhythmic therapy 2
   • Review and optimize ICD programming 2

Special Considerations

• Multiple VT morphologies are common in patients with extensive structural heart disease 2
• Electrical storm (≥3 episodes of sustained VT within 24 hours) requires urgent intervention 2
• Cardiac sarcoidosis requires a tailored approach based on disease phase (inflammatory vs. scar) 5
• Noninvasive ECG imaging can help map unstable VTs and identify critical ablation sites 6

In patients with scar-related VT, a comprehensive management approach including catheter ablation, antiarrhythmic medications, and ICD therapy significantly improves outcomes by reducing VT recurrence, ICD shocks, and improving quality of life.