Wolff-Parkinson-White (WPW) Syndrome

Snapshot

• 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.

Introduction

• 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 orthodromic AVRT
        • narrow QRS complexes
      • less commonly as (5%) antidromic AVRT
        • wide QRS complexes (> 120 ms)
    • atrial fibrillation
    • atrial flutter
    • ventricular tachycardia
• ventricular fibrillation and sudden death

Presentation

• Symptoms
  • can be asymptomatic
  • if symptomatic, patients will present with
    • palpitations 
    • lightheadedness
    • syncope
    • dizziness
    • chest pain
• Physical exam
• tachycardia

Studies

• 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

Differential

• Bundle branch block
  • distinguishing factor
• widened and abnormal terminal portion of QRS portion on ECG

Treatment

• 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

Complications

• Sudden cardiac death