• A 10-year-old boy presents to the pediatrician’s office for an electrocardiogram. His family history includes Wolff-Parkinson-White syndrome and sudden cardiac death. His parents are adamant about an electrocardiogram at this visit. Results show a widened QRS, a delta wave, and a shortened PR interval, confirming the diagnosis.
  • Clinical definition
    • a ventricular pre-excitation syndrome resulting in an aberrant conduction tract that bypasses the atrioventricular (AV) node 
  • Epidemiology
    • risk factors
      • family history
  • Etiology
    • can be familial
  • Pathogenesis
    • ventricular pre-excitation results from an aberrant conduction tract from the atria to the ventricle, known as the bundle of Kent
      • this fast accessory tract bypasses the AV node
      • ventricles then depolarize earlier than normal
      • this causes the classic delta wave and widened QRS
    • administration of calcium channel blockers or digoxin will worsen a supraventricular tachycardia (SVT) caused by WPW syndrome
      • these medications block conduction in the AV node and will force more conduction down the aberrant tract, worsening WPW syndrome
  • Associated conditions
    • Ebstein anomaly
    • hypertrophic cardiomyopathy
  • Prognosis
    • can present with
      • atrioventricular reentrant tachycardia (AVRT)
        • most commonly as antidromic AVRT
          • wide QRS complexes
        • less commonly as (5%) orthodromic AVRT
          • narrow QRS complexes (< 120 ms)
      • atrial fibrillation
      • atrial flutter
      • ventricular tachycardia
      • ventricular fibrillation and sudden death
  • Symptoms
    • can be asymptomatic
    • if symptomatic, patients will present with
      • palpitations
      • lightheadedness
      • syncope
      • dizziness
      • chest pain
  • Physical exam
    • tachycardia
  • Electrocardiogram (ECG)  
    • delta wave
    • short PR interval
    • widened QRS complex
    • may have supraventricular tachycardia if symptomatic
  • Making the diagnosis
    • based on clinical presentation and ECG
  • Bundle branch block
    • distinguishing factor
      • widened and abnormal terminal portion of QRS portion on ECG
  • Management approach
    • drugs that delay AV node conduction is typically contraindicated in these patients unless patients have confirmed orthodromic AVRT
  • Medical
    • procainamide
      • indications
        • for patients who are hemodynamically stable
        • for patients with antidromic AVRT or atrial fibrillation due to WPW syndrome
    • adenosine or calcium channel blocker
      • indication
        • for patients with orthodromic AVRT (narrow QRS complexes)
  • Non-operative
    • electrical cardioversion
      • indication
        • for all patients who are hemodynamically unstable due to arrhythmia
    • radiofrequency catheter ablation
      • indication
        • long-term definitive therapy for patients with WPW syndrome
  • Sudden cardiac death

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