What is the drug of choice for stable antidromic atrioventricular reentrant tachycardia (AVRT) associated with Wolff-Parkinson-White (WPW) syndrome?

Drug of Choice for Stable Antidromic AVRT in WPW Syndrome

For stable antidromic atrioventricular reentrant tachycardia (AVRT) associated with Wolff-Parkinson-White (WPW) syndrome, ibutilide, procainamide, or flecainide are the preferred pharmacological agents as they effectively slow conduction through the accessory pathway. 1, 2

Pharmacological Management Algorithm

First-line agents:

• Ibutilide (IV): Recommended as first-line therapy for stable patients with antidromic AVRT due to its ability to slow conduction through the accessory pathway 1, 2
• Procainamide (IV): Equally effective first-line option that slows conduction through the accessory pathway and can terminate the tachyarrhythmia 1, 2
• Flecainide (IV): Alternative first-line agent that effectively slows accessory pathway conduction 1, 2

Second-line agents:

• Propafenone: Class IC antiarrhythmic that reduces conduction and increases the effective refractory period of the accessory pathway in both directions 3, 4
• Disopyramide or Quinidine: Class IA antiarrhythmics that may be considered if first-line agents are unavailable or ineffective 1, 2

Critical Contraindications

• AVOID AV nodal blocking agents in patients with WPW and antidromic AVRT as they can paradoxically increase conduction through the accessory pathway, potentially precipitating ventricular fibrillation 1, 2
• Specifically contraindicated medications include:
  • Beta-blockers 1, 2
  • Calcium channel blockers (diltiazem, verapamil) 1, 2
  • Digoxin 1, 2
  • Adenosine (should be used with extreme caution as it may precipitate atrial fibrillation with rapid ventricular response) 1

Mechanism of Action

• Ibutilide, procainamide, and flecainide work by slowing conduction through the accessory pathway, which is the critical component in antidromic AVRT 1
• In antidromic AVRT, the accessory pathway serves as the antegrade limb of the circuit while the AV node serves as the retrograde limb 5
• These agents increase the refractory period of the accessory pathway, thereby interrupting the reentrant circuit 3, 4

Special Considerations

• Antidromic AVRT is rare, occurring in less than 5% of patients with WPW syndrome clinically and is inducible in less than 10% of WPW cases in electrophysiology studies 5
• If pharmacological therapy fails or the patient becomes hemodynamically unstable, synchronized cardioversion is recommended 1
• After acute management, catheter ablation of the accessory pathway should be considered as definitive treatment, with success rates >95% in experienced centers 1, 2

Monitoring and Follow-up

• Even after successful acute treatment, patients should be evaluated for definitive management with catheter ablation 2
• Patients with WPW syndrome who have experienced antidromic AVRT are at risk for recurrent episodes and potentially life-threatening arrhythmias 1
• Risk factors for sudden cardiac death in WPW include shortest pre-excited R-R interval <250 ms during atrial fibrillation, multiple accessory pathways, and history of symptomatic tachycardia 1

Remember that while pharmacological therapy can effectively terminate acute episodes of antidromic AVRT, catheter ablation remains the definitive treatment of choice for symptomatic patients with WPW syndrome 1, 2, 6.