What medications are contraindicated in Wolff-Parkinson-White (WPW) syndrome?

Medications Contraindicated in Wolff-Parkinson-White Syndrome

Digitalis glycosides (digoxin) and non-dihydropyridine calcium channel antagonists (verapamil, diltiazem) are absolutely contraindicated in patients with Wolff-Parkinson-White syndrome, particularly during atrial fibrillation, as they can accelerate ventricular rate and potentially cause ventricular fibrillation. 1

Mechanism of Danger in WPW

Wolff-Parkinson-White syndrome is characterized by the presence of an accessory pathway (bypass tract) that allows electrical impulses to bypass the AV node and directly activate the ventricles. This creates specific risks with certain medications:

• AV nodal blocking agents can paradoxically increase conduction through the accessory pathway by:
  • Slowing conduction through the normal AV node
  • Creating preferential conduction through the accessory pathway
  • Potentially leading to extremely rapid ventricular rates during atrial fibrillation
  • Increasing risk of ventricular fibrillation and sudden cardiac death

Specific Contraindicated Medications

1. Digitalis glycosides (digoxin) 1

   • Class III: Harm (potentially dangerous)
   • Can facilitate anterograde conduction along the accessory pathway
   • May accelerate ventricular response during atrial fibrillation

2. Non-dihydropyridine calcium channel antagonists 1, 2

   • Verapamil
   • Diltiazem
   • FDA-labeled contraindication for verapamil: "Patients with atrial flutter or atrial fibrillation and an accessory bypass tract (e.g., Wolff-Parkinson-White, Lown-Ganong-Levine syndromes)" 2

3. Adenosine 3

   • Can cause similar effects as other AV nodal blocking agents
   • Potentially harmful in patients with pre-excited atrial fibrillation

4. Amiodarone (IV) 1

   • While sometimes used in stable patients, IV amiodarone is potentially harmful when WPW patients have pre-excited atrial fibrillation

Safe Medications for WPW

For patients requiring medication management:

1. For rhythm control in hemodynamically stable patients:

   • Procainamide (IV) 1
   • Ibutilide (IV) 1
   • Flecainide 1
   • Class IA antiarrhythmics (quinidine, disopyramide) 1

2. For emergency management:

   • Direct-current cardioversion is first-line for hemodynamically unstable patients 1

Critical Management Points

• Definitive treatment: Catheter ablation of the accessory pathway is the recommended first-line treatment for symptomatic patients with WPW 1, 3

• Emergency management: Immediate direct-current cardioversion for patients with rapid ventricular response and hemodynamic instability 1

• Risk assessment: Patients with short refractory periods of the accessory pathway (<250 ms) are at higher risk for sudden cardiac death 3

Clinical Pitfalls to Avoid

1. Never administer AV nodal blocking agents to patients with known or suspected WPW who present with atrial fibrillation or flutter

2. Do not assume beta-blockers are safe in all WPW patients - they may be harmful in patients with pre-excited atrial fibrillation

3. Avoid misdiagnosing WPW - look for delta waves on ECG before administering rate-controlling medications for atrial fibrillation

4. Do not delay cardioversion in hemodynamically unstable patients while attempting pharmacological management

By strictly avoiding AV nodal blocking agents in patients with WPW, particularly during episodes of atrial fibrillation, the risk of life-threatening arrhythmias can be significantly reduced.