Wolff–Parkinson–White syndrome

Background

• Orthodromic (~95%)
  • Accessory pathway 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%

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 vent 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
• Procainamide 100mg q10min until disrhythmia terminated or max dose (1000mg)
  • Amiodarone
  • Cardioversion
    • Adult: 50-100 J
    • Peds: 0.5- 2 J/kg
  • Contraindicated: CCBs, BBs, digoxin, adenosine

• Irregular tachycardia
  • Treat like antidromic

Disposition

• Admission:
  • Cardioverted, chest pain, CHF, or electrolyte imbalance
• Discharge
  • If easily terminated d/c w/ outpt EP study