What are the management options for supraventricular tachycardia (SVT) in patients with Wolff-Parkinson-White (WPW) syndrome?

Management of SVT in Wolff-Parkinson-White Syndrome

In patients with Wolff-Parkinson-White (WPW) syndrome, catheter ablation of the accessory pathway is the first-line treatment for symptomatic patients, particularly those with pre-excited atrial fibrillation or accessory pathways with short refractory periods (<250 ms). 1

Types of SVT in WPW Syndrome

1. Orthodromic AVRT

• Most common arrhythmia (95% of reentrant tachycardias in WPW) 2
• Conduction travels anterograde through AV node and retrograde through accessory pathway
• Presents with narrow QRS complexes unless aberrant conduction occurs
• Regular rhythm with heart rates typically 150-250 bpm

2. Antidromic AVRT

• Less common (5% of reentrant tachycardias in WPW)
• Conduction travels anterograde through accessory pathway and retrograde through AV node
• Presents with wide QRS complexes due to ventricular pre-excitation
• Regular rhythm with heart rates typically 170-250 bpm

3. Pre-excited Atrial Fibrillation

• Most dangerous arrhythmia in WPW
• Rapid conduction over accessory pathway can lead to ventricular fibrillation
• Irregular wide-complex tachycardia with variable RR intervals
• Risk of sudden cardiac death (0.15-0.39% over 3-10 years) 2

4. Permanent Junctional Reciprocating Tachycardia (PJRT)

• Rare form involving a concealed, slowly conducting posteroseptal accessory pathway
• Characterized by incessant SVT with negative P waves in leads II, III, aVF
• Long RP interval (RP > PR) 2

Acute Management Algorithm

For Hemodynamically Unstable Patients:

1. Immediate synchronized cardioversion regardless of SVT type 2
   • Start with 100 J, increase in stepwise fashion if needed 2
   • Particularly critical for pre-excited AF 2

For Hemodynamically Stable Patients with Orthodromic AVRT:

1. First-line: Vagal maneuvers (Valsalva, carotid sinus massage) 2

   • Success rate up to 27.7% 2

2. Second-line: Adenosine

   • Effective in 90-95% of orthodromic AVRT cases 2
   • Start with 6 mg IV push, followed by 12 mg if no response 2
   • Have defibrillator available as adenosine may precipitate AF 2

3. If adenosine fails: Synchronized cardioversion 2

For Hemodynamically Stable Patients with Pre-excited AF:

1. First-line: IV procainamide or ibutilide 2, 1

   • These medications slow conduction over the accessory pathway and may terminate AF

2. If medications fail: Synchronized cardioversion 2

Critical Warning:

AV nodal blocking agents (diltiazem, verapamil, digoxin, beta-blockers, adenosine) are contraindicated in pre-excited AF as they can accelerate ventricular rate by preferential conduction through the accessory pathway, potentially causing ventricular fibrillation. 1

Long-term Management

1. Catheter Ablation

• First-line therapy for symptomatic WPW patients 1
• Success rates >95% with low complication rates
• Particularly indicated for:
  • Patients with pre-excited AF
  • Syncope suggesting rapid heart rates
  • Accessory pathways with short refractory periods (<250 ms)
  • Multiple accessory pathways
  • History of symptomatic tachycardia

2. Pharmacological Therapy (if ablation not feasible)

• For orthodromic AVRT:

  • Class Ia, Ic, or III antiarrhythmic agents that alter conduction through the accessory pathway
  • Beta-blockers may be used if accessory pathway has been demonstrated to be incapable of rapid anterograde conduction 2

• For pre-excited AF:

  • Class Ia (procainamide) or Ic antiarrhythmic agents
  • Amiodarone may be considered

Risk Stratification for Sudden Cardiac Death

High-risk features include:

• Shortest pre-excited R-R interval <250 ms during AF
• History of symptomatic tachycardia
• Multiple accessory pathways
• Ebstein's anomaly 2

Post-Ablation Monitoring

• ECG assessment at 3 months post-procedure
• Annual ECG for first few years
• Patient education regarding symptoms that warrant immediate medical attention 1
• Approximately 5-10% of patients may experience recurrence of accessory pathway conduction 1

Pitfalls to Avoid

1. Never use AV nodal blocking agents (adenosine, beta-blockers, calcium channel blockers, digoxin) in patients with suspected pre-excited AF - this can accelerate conduction through the accessory pathway and precipitate ventricular fibrillation

2. Don't assume WPW is benign in asymptomatic patients - approximately 25% of WPW patients have accessory pathways with short anterograde refractory periods (<250 ms) that can lead to sudden cardiac death 1

3. Don't forget that ablation of the accessory pathway doesn't prevent future atrial fibrillation - especially in older patients, with about 15% risk of developing AF over 10 years 1

4. Recognize that septal pathway locations have higher complication rates during ablation (9.1% vs 2.0% for left-sided pathways) 1