What is the emergency treatment to convert Wolff-Parkinson-White (WPW) tachycardia?

Emergency Treatment for Wolff-Parkinson-White (WPW) Tachycardia

For emergency treatment of WPW tachycardia, synchronized cardioversion is recommended for hemodynamically unstable patients, while hemodynamically stable patients with pre-excited atrial fibrillation should receive IV procainamide or ibutilide as first-line pharmacological therapy. 1, 2

Initial Assessment and Treatment Algorithm

Hemodynamically Unstable Patients

1. Immediate synchronized cardioversion (Class I, LOE B-NR) 1
   • Should be performed without delay for patients with:
     • Hypotension
     • Altered mental status
     • Signs of shock
     • Chest pain
     • Acute heart failure

Hemodynamically Stable Patients

Treatment depends on the specific type of WPW tachycardia:

For Orthodromic AVRT (narrow complex tachycardia):

1. Vagal maneuvers (Class I, LOE B-R) 1, 2

   • Valsalva maneuver (most effective)
   • Carotid sinus massage (after confirming absence of bruits)
   • Application of cold to face

2. Adenosine if vagal maneuvers fail (Class I, LOE B-R) 1

   • 6 mg rapid IV push through large vein with 20 mL saline flush
   • If ineffective after 1-2 minutes, give 12 mg IV push
   • CAUTION: Have defibrillator immediately available as adenosine may precipitate atrial fibrillation

3. Synchronized cardioversion if pharmacological therapy fails (Class I, LOE B-NR) 1

For Pre-excited Atrial Fibrillation (irregular wide-complex tachycardia):

1. IV procainamide or ibutilide (Class I, LOE B-R) 1, 2, 3

   • Procainamide: 20 mg/min infusion up to 15 mg/kg (typically 1 gram)
   • Monitor for QRS widening, QT prolongation, and hypotension

2. Synchronized cardioversion if pharmacological therapy fails or if patient becomes unstable 1

Critical Contraindications

NEVER ADMINISTER the following medications in WPW with pre-excited atrial fibrillation 2:

• AV nodal blocking agents:
  • Diltiazem
  • Verapamil
  • Beta-blockers
  • Digoxin
  • Adenosine
• Amiodarone

These medications can accelerate conduction through the accessory pathway, potentially precipitating ventricular fibrillation and sudden cardiac death.

Monitoring and Follow-up

• Continuous cardiac monitoring during and after conversion
• Assess for recurrence of arrhythmia
• Consider referral for electrophysiology study and catheter ablation, which has >95% success rate 2
• High-risk features warranting urgent referral:
  • Short refractory period of accessory pathway (<250 ms)
  • Multiple accessory pathways
  • History of pre-excited atrial fibrillation
  • Associated cardiac anomalies (e.g., Ebstein's anomaly)

Pitfalls to Avoid

1. Misdiagnosis: WPW with pre-excited AF can mimic ventricular tachycardia - careful ECG interpretation is essential
2. Inappropriate medication use: AV nodal blocking agents can be fatal in pre-excited AF
3. Delayed cardioversion: Don't hesitate to perform synchronized cardioversion in unstable patients
4. Inadequate monitoring: All patients require continuous cardiac monitoring during treatment
5. Failure to arrange definitive treatment: Most patients with symptomatic WPW should be referred for catheter ablation

The emergency management of WPW tachycardia requires rapid assessment, appropriate medication selection based on the specific arrhythmia mechanism, and readiness for electrical cardioversion when necessary. Recognizing pre-excited atrial fibrillation is particularly critical as inappropriate medication choices can lead to ventricular fibrillation and sudden death.