What is the role of Electrophysiological Studies (EPS) in the management of Right Ventricular Outflow Tract (RVOT) Ventricular Tachycardia (VT)?

Role of Electrophysiological Studies in RVOT Ventricular Tachycardia

Electrophysiological studies (EPS) are reasonable and recommended for diagnostic evaluation in patients with structurally normal hearts who have palpitations or suspected right ventricular outflow tract ventricular tachycardia (RVOT VT). 1

Diagnostic Value of EPS in RVOT VT

EPS serves several critical purposes in the management of RVOT VT:

1. Precise Diagnosis and Localization:

   • EPS is motivated primarily by the need to establish precise diagnosis to guide curative catheter ablation 1
   • Activation mapping and/or pacemapping during EPS allows precise localization of the VT origin 1
   • Mapping should begin in the RVOT (including pulmonary artery sinus), followed by great cardiac veins, aortic cusps, and endocardial LVOT 1

2. Mechanism Identification:

   • EPS helps differentiate RVOT VT from more serious conditions like arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) 1
   • RVOT VT typically demonstrates triggered activity arising from delayed afterdepolarizations 1
   • The arrhythmia is frequently adenosine-sensitive and facilitated by catecholamines 1

3. Induction of Arrhythmia:

   • RVOT VT is often not easily inducible at baseline EP testing 1
   • May require specific protocols:
     • Rapid burst pacing 1
     • Isoproterenol infusion (can increase inducibility from 3% to 80%) 1

EPS as Guide for Ablation Therapy

When medical therapy fails or patients remain symptomatic, EPS plays a crucial role in guiding ablation:

1. Mapping for Ablation:

   • The 2015 ESC guidelines recommend catheter ablation of RVOT VT/PVCs in:
     • Symptomatic patients
     • Patients with failure of anti-arrhythmic drug therapy
     • Patients with LV function decline due to RVOT-PVC burden 1

2. Ablation Success Rates:

   • Acute success rates for RVOT ablation exceed 95% when performed by experienced operators 1
   • Long-term success varies, with recurrence rates of approximately 50% over extended follow-up 2
   • Recurrences may have similar morphology (33%) or different morphology (67%) compared to the initially treated arrhythmia 2

Clinical Approach to RVOT VT Management

Based on the evidence, a structured approach to RVOT VT management incorporating EPS includes:

1. Initial Assessment:

   • ECG characteristics: Left bundle branch block morphology with inferior axis 1
   • Rule out structural heart disease through imaging (echocardiography, MRI) 1

2. First-line Treatment:

   • Medical therapy with beta-blockers and/or calcium channel blockers 1
   • Class IC antiarrhythmic drugs are particularly useful in RVOT VT 1

3. When to Consider EPS and Ablation:

   • For patients who:
     • Remain symptomatic despite medical therapy
     • Are drug-intolerant
     • Do not desire long-term drug therapy
     • Show LV function decline due to high PVC burden 1

4. Post-ablation Follow-up:

   • Long-term monitoring is necessary due to potential late recurrences 2
   • Recurrent symptoms warrant repeat evaluation

Important Considerations and Pitfalls

1. Differentiating from ARVD/C:

   • Electrophysiological characterization is crucial to differentiate RVOT VT from ARVD/C 3
   • ARVD/C typically displays re-entry mechanisms (>80%), while RVOT VT shows triggered activity in 97% of cases 3
   • Misdiagnosis can lead to inappropriate treatment strategies

2. Limitations of EPS:

   • Standard EP protocols may fail to induce RVOT VT
   • Always consider isoproterenol infusion if initial induction attempts fail 1
   • Some cases may represent epicardial foci, requiring specialized approaches 4

3. Ablation Challenges:

   • Anatomical complexity may require specialized mapping techniques
   • LVOT ablation should only be performed in highly experienced centers 1
   • Potential complications include RVOT rupture (rare), myocardial rupture, tamponade, stroke, valvular damage, and coronary artery damage 1

In conclusion, EPS plays a vital diagnostic and therapeutic role in RVOT VT management, particularly in guiding curative catheter ablation, which has become the definitive treatment for drug-refractory cases or patients who prefer not to take long-term medications.