Can adenosine be given to patients with Wolff-Parkinson-White (WPW) syndrome?

Adenosine in Wolff-Parkinson-White Syndrome

Adenosine should NOT be administered to patients with Wolff-Parkinson-White (WPW) syndrome who have pre-excited atrial fibrillation as it can accelerate conduction through the accessory pathway, potentially precipitating ventricular fibrillation and sudden cardiac death. 1

Safety of Adenosine in WPW: A Nuanced Approach

The safety of adenosine in WPW depends on the specific arrhythmia present:

When Adenosine is Contraindicated:

• In WPW with pre-excited atrial fibrillation or flutter
  • AV nodal blocking agents (including adenosine) are Class III: Harm (Level of Evidence: B) 1
  • These agents can preferentially block the AV node, allowing faster conduction through the accessory pathway 2
  • This can lead to ventricular fibrillation and sudden cardiac death 1

When Adenosine May Be Used:

• In narrow QRS complex tachycardia (< 120 ms) 2
  • This indicates antegrade conduction is occurring through the AV node, not the accessory pathway
  • A defibrillator should be immediately available as adenosine may precipitate atrial fibrillation 2, 1
• After vagal maneuvers have failed in hemodynamically stable patients 2, 1
  • Dosing: 6 mg rapid IV push through a large vein with 20 mL saline flush
  • If ineffective, may give 12 mg 2

Emergency Management Algorithm for WPW Tachycardia

1. Assess hemodynamic stability

   • If unstable: Immediate synchronized cardioversion (Class I, LOE B-NR) 1

2. If stable with regular narrow QRS tachycardia:

   • Try vagal maneuvers first (Class I, LOE B-R) 2, 1
   • If vagal maneuvers fail and QRS < 120 ms: Adenosine may be used 2
   • Have defibrillator immediately available 2, 1

3. If stable with wide QRS tachycardia or pre-excited atrial fibrillation:

   • DO NOT use adenosine, diltiazem, verapamil, beta-blockers, or digoxin 2, 1
   • Use IV procainamide or ibutilide (Class I, LOE B-R) 2, 1
   • Procainamide: 20 mg/min infusion up to 15 mg/kg (typically 1 gram) 1
   • Monitor for QRS widening, QT prolongation, and hypotension 1

Critical Pitfalls to Avoid

1. Never administer AV nodal blocking agents (adenosine, diltiazem, verapamil, beta-blockers, digoxin) to WPW patients with pre-excited atrial fibrillation 2, 1

2. ECG interpretation is crucial before giving adenosine:

   • Narrow QRS (< 120 ms): May consider adenosine
   • Wide QRS (≥ 120 ms): Avoid adenosine 2

3. Always have a defibrillator immediately available when administering adenosine to any patient with suspected WPW 2, 1

4. Recognize high-risk WPW features that warrant more aggressive management:

   • 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) 1

Definitive Management

For long-term management, catheter ablation is recommended for symptomatic patients with WPW syndrome, particularly those with syncope due to rapid heart rate or those with short bypass tract refractory periods, with success rates exceeding 95% 2, 1.