Wolff–Parkinson–White syndrome

Background

• Orthodromic (~95%)
  • Accessory pathway (Kent bundles) is used for retrograde reentry conduction
    • QRS narrow (delta wave absent)
    • May see ST depression, TWI
    • Rate 150-250 bpm
• Antidromic (~5%)
  • Accessory pathway used for anterograde conduction
    • QRS wide, delta wave present

• Atrial fibrillation seen in 10-30%
• Ventricular rate >300 suggests preexcitation

Diagnosis

• Characteristic features not always seen on ECG

1. Short PR interval - <0.12sec
   1. Due to loss of normal AV node conduction delay
2. Delta wave / slurred upstroke
   1. Due to early activation of ventricular myocardium
3. QRS duration > 0.10 sec
   1. Due to delta wave

Treatment

• Orthodromic
  • Treat like paroxysmal SVT
    • CCBs, BBs, procainamide, or adenosine
    • Procainamide safe irrespective of type of pathway conduction
    • Cardiovert (sync) if unstable
    • Adult: 50-100 J
    • Peds: 0.5- 2 J/kg

• Antidromic
  • Treat like ventricular tachycardia
    • Contraindicated: CCBs, BBs, digoxin, adenosine
  • Cardioversion (synchronized)
    • Adult: 50-100 J
    • Peds: 0.5- 2 J/kg
  • Procainamide 100mg q10min until dysrhythmia terminated or max dose (1000mg)
  • Amiodarone

• Irregular tachycardia
  • Treat like antidromic

Disposition

• Admit:
  • Pts with chest pain, CHF, electrolyte imbalance, or required cardioversion
• Discharge:
  • Consider if dysrhythmia was easily terminated and can arrange outpt EP study