Can adenosine worsen Wolff-Parkinson-White (WPW) syndrome?

Adenosine Can Worsen Wolff-Parkinson-White Syndrome

Adenosine is contraindicated in patients with Wolff-Parkinson-White syndrome as it can potentially worsen the condition by precipitating life-threatening ventricular arrhythmias. 1, 2

Mechanism of Harm

Adenosine works by blocking conduction through the AV node, which in normal patients helps terminate supraventricular tachycardias. However, in WPW patients, this mechanism creates a dangerous situation:

• Adenosine blocks the normal AV nodal pathway but does not affect the accessory pathway
• This promotes preferential conduction through the accessory pathway
• If atrial fibrillation develops, rapid conduction through the accessory pathway can occur
• This can lead to extremely fast ventricular rates and potentially degenerate into ventricular fibrillation

Evidence-Based Recommendations

The American College of Cardiology/American Heart Association/European Society of Cardiology guidelines explicitly state that adenosine should not be administered to patients with WPW syndrome who have pre-excited atrial fibrillation, classifying this as a Class III: Harm recommendation with Level of Evidence B. 1

The FDA drug label for adenosine also warns about the risk of ventricular arrhythmias following adenosine administration. 2

Proper Management of WPW with Arrhythmias

For patients with WPW presenting with arrhythmias, the following approach is recommended:

Hemodynamically Unstable Patients

• Immediate direct-current cardioversion is the first-line treatment (Class I recommendation) 1, 3

Hemodynamically Stable Patients

• For pre-excited atrial fibrillation:
  • IV procainamide or ibutilide are the preferred medications (Class I recommendation) 1, 3
  • These agents slow conduction through the accessory pathway

Contraindicated Medications in WPW

• Adenosine (Class III: Harm) 1, 3
• Digoxin (Class III: Harm) 1, 3
• Non-dihydropyridine calcium channel blockers (verapamil, diltiazem) (Class III: Harm) 1
• Beta-blockers (Class III: Harm) 1, 3

Definitive Management

Catheter ablation of the accessory pathway is recommended for all symptomatic patients with WPW syndrome, especially those with:

• History of syncope
• Short accessory pathway refractory period (<250 ms)
• Multiple accessory pathways 3

Clinical Pearls and Pitfalls

• A defibrillator should always be available when administering adenosine to any patient in whom WPW is a consideration 1
• Some WPW accessory pathways are adenosine-sensitive (approximately 15% of cases), but this should not be used as a therapeutic strategy 4, 5
• In emergency situations where WPW is not recognized, administration of adenosine can unmask the condition by increasing the degree of pre-excitation, which may aid in diagnosis but can also precipitate dangerous arrhythmias 4
• The risk of sudden cardiac death in untreated WPW ranges from 0.15% to 0.6% per year, with the highest risk in the first two decades of life 3

Remember that proper identification of WPW on ECG (short PR interval, delta wave, and wide QRS complex) is crucial before administering any AV nodal blocking agent, including adenosine.