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

DDX

1. idiopathic
2. hypertrophic cardiomyopathy
3. transposition of great vesses
4. endocardial fibroelastosis
5. mitral valve prolapse
6. tricuspid atresia
7. ebstein disease

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