Wolff–Parkinson–White syndrome

Background

• Suspect in any pt w/ ventricular rate >300

Orthodromic Type

• More common type occuring ~95% of the time
• 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 Type

• Least common type occuring ~5% of the time
• Accessory pathway used for anterograde conduction
• QRS wide, delta wave present

Diagnosis

Although the ECG and an electrophysiology study are diagnostic, the characteristic features are 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
4. Dominant R wave in V1, Type A WPW
   1. Left sided accessory pathway
5. Dominant S wave in V1, Type B WPW
   1. Right sided accessory pathway
6. Tall R waves in V1-V3 with T wave inversion
   1. Mimic RVH
7. "Negative" delta waves in III and aVF
   1. Appear as pseudo-infarct Q waves
   2. Mimics prior inferior infarct

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 with 'ABCD' drugs ie adenosine, BBs, CCBs, digoxin
• Wide-complex, irregular (presumed preexcited A-fib)
  • Unsynchronized cardioversion (200J)

Disposition

• Discharge:
  • Consider if dysrhythmia was easily terminated and can arrange outpt EP study with poss RF catheter ablation
  • C/w with cardiologist regarding outpt beta-blockers vs. more potent medications (amiodarone, sotalol, flecainide, etc.)
• Admit or transfer to center with electrophys:
  • Pts with chest pain, CHF, electrolyte imbalance, or required cardioversion
  • Syncope
  • Uncertain dx (wide-complex tachycardia)
  • Significant associated structural heart disease (MVP, cardiomyopathy)
  • Family hx of Sudden cardiac death
  • Atrial flutter or atrial fibrillation

See Also

• SVT

Sources

• Burns E. Pre-excitation Syndromes. Life in the Fast Lane. http://lifeinthefastlane.com/ecg-library/pre-excitation-syndromes/.