Wolff–Parkinson–White syndrome

Background

• Suspect in any pt w/ ventricular rate >300

Types

• 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

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. Differentiate from premature junctional complex
2. Delta wave / slurred upstroke
   1. Due to early activation of ventricular myocardium
3. QRS duration > 0.10 sec
   1. Represents a fusion beat

Treatment

• Orthodromic
  • Treat like paroxysmal SVT:
    • Unstable
      • Cardioversion (synchronized)
        • Adult: 50-100 J
        • Peds: 0.5-2 J/kg
    • Stable
      • CCBs, BBs, procainamide, or adenosine
        • Procainamide safe irrespective of type of pathway conduction
• Antidromic
  • Treat like ventricular tachycardia:
    • Synchronized cardioversion
      • Adult: 50-100 J
      • Peds: 0.5-2 J/kg
    • Procainamide
      • 17mg/kg IV over 30min (up to 50mg/kg or 50% widening of QRS complex)
    • Amiodarone
    • Contraindicated: 'ABCD' drugs ie adenosine, BBs, CCBs, digoxin
• Wide-complex, irregular (presumed preexcited A-fib)
  • Unsynchronized cardioversion (200J)

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

See Also

• SVT