What is the management approach for a patient with right bundle branch block (RBBB) tachycardia?

Management of Right Bundle Branch Block Tachycardia

The management of right bundle branch block (RBBB) tachycardia should focus on identifying the underlying mechanism and providing appropriate treatment based on hemodynamic stability, with wide complex tachycardias being treated as ventricular tachycardia when the diagnosis is uncertain. 1

Initial Assessment and Stabilization

Hemodynamic Status Evaluation

• Hemodynamically unstable patients (hypotension, angina, heart failure, altered mental status):

  • Immediate synchronized direct current (DC) cardioversion is recommended (Class I) 1
  • Apply transcutaneous pacing pads as standby before cardioversion

• Hemodynamically stable patients:

  • Obtain 12-lead ECG to determine specific mechanism
  • Look for signs of VA dissociation, fusion beats, or capture beats that would confirm VT

Diagnostic Considerations

Key Differentiating Features

• QRS width: >0.14 seconds with RBBB pattern favors VT 1
• VA dissociation: Strongly suggests VT but only visible in about 30% of cases 1
• RS interval: >100 ms in any precordial lead is highly suggestive of VT 1
• Fusion complexes: Pathognomonic of VT 1

Common RBBB Tachycardia Mechanisms

1. Ventricular tachycardia (treat as VT if diagnosis uncertain)
2. Supraventricular tachycardia with aberrancy:
   • Pre-existing RBBB
   • RBBB due to rate-related aberrant conduction
3. Bundle branch reentrant tachycardia:
   • Involves right bundle branch as anterograde and left bundle branch as retrograde limb 1
   • Often associated with cardiomyopathy
4. Antidromic AVRT:
   • Conduction over an accessory pathway (especially atriofascicular pathway)

Management Based on Specific Diagnosis

1. Ventricular Tachycardia with RBBB Morphology

• First-line treatment:

  • IV amiodarone 150mg over 10 minutes (for stable patients) 1
  • Consider IV procainamide or sotalol as alternatives
  • Synchronized cardioversion for unstable patients

• Long-term management:

  • ICD implantation for patients with structural heart disease and reduced ejection fraction (<45%) 1
  • Catheter ablation for recurrent episodes, especially in patients with ICD shocks 1

2. Bundle Branch Reentrant Tachycardia

• First-line treatment:
  • Catheter ablation of the right bundle branch (Class I recommendation) 1, 2
  • ICD placement should be strongly considered as the underlying structural abnormality remains 1
  • Excellent survival rates when other types of VT are also treated 2

3. SVT with RBBB Aberrancy

• Acute treatment:

  • Vagal maneuvers first (Class I) 1
  • Adenosine 6-12mg IV rapid push (Class I) 1, 3
  • Non-dihydropyridine calcium channel blockers (diltiazem, verapamil) or beta-blockers if adenosine fails 1

• Long-term management:

  • Treat underlying SVT mechanism
  • Consider catheter ablation for recurrent episodes

4. RBBB Tachycardia in Specific Conditions

• Tetralogy of Fallot:

  • RBBB is common in post-repair patients
  • VT often arises from right ventricular outflow tract 1
  • Electrophysiological testing may be required for diagnosis 1

• Ebstein's Anomaly:

  • RBBB is usually present and may be masked by ventricular pre-excitation 1
  • Coordinate arrhythmia management with surgical team if operative correction is planned 1

• Arrhythmogenic Right Ventricular Cardiomyopathy:

  • RBBB VT can originate from either RV (62%) or LV (38%) 4
  • Precordial R-wave transition and frontal plane axis help identify chamber of origin 4

Important Cautions and Pitfalls

• When diagnosis is uncertain, always treat wide QRS-complex tachycardia as VT 1, 5
• Avoid AV nodal blocking agents (calcium channel blockers, beta-blockers) in patients with pre-excited AF as they can accelerate ventricular rate and cause ventricular fibrillation 5
• Use caution with flecainide as it can worsen CHF, slow cardiac conduction, and increase PR, QRS, and QT intervals 6
• Monitor for development of complete heart block after right bundle branch ablation, especially in patients with pre-existing conduction disease 2

Follow-up Considerations

• Evaluate for structural heart disease with echocardiography or cardiac MRI
• Consider electrophysiology study for definitive diagnosis and potential ablation
• Assess need for ICD based on ejection fraction and underlying heart disease
• Regular monitoring for recurrence and progression of conduction disease