Pediatric Wolff-Parkinson-White (WPW) Syndrome

Wolff-Parkinson-White (WPW) syndrome is a congenital pre-excitation cardiac arrhythmia characterized by the presence of an accessory electrical pathway between the atria and ventricles, which can lead to rapid and potentially life-threatening tachyarrhythmias.

Key Points

• Estimated prevalence of 0.1-0.3% in the general population
• Can manifest at any age, including infancy and early childhood
• If untreated, can increase the risk of sudden cardiac death
• Early recognition and appropriate management are crucial

Pathophysiology

Accessory Electrical Pathway

• Presence of an abnormal, anomalous electrical connection (accessory pathway) between the atria and ventricles
• This pathway bypasses the normal atrioventricular (AV) node conduction system
• Allows for rapid, uncontrolled conduction of electrical impulses, leading to tachyarrhythmias

Mechanisms of Tachyarrhythmias

• Anterograde conduction: Electrical impulses travel from the atria to the ventricles via the accessory pathway, causing a pre-excited QRS complex on ECG
• Retrograde conduction: Electrical impulses travel from the ventricles back to the atria via the accessory pathway, leading to atrioventricular reentrant tachycardia (AVRT)
• Atrial fibrillation: Rapid, irregular atrial activity can degenerate into ventricular fibrillation if the accessory pathway allows rapid conduction to the ventricles

Clinical Presentation

Asymptomatic Patients

• Some individuals with WPW may remain asymptomatic throughout their lives
• Accessory pathway may be identified incidentally on ECG

Symptomatic Patients

• Palpitations: Sudden onset of rapid, regular heart rate
• Chest pain or discomfort
• Lightheadedness, dizziness, or syncope
• Shortness of breath
• In severe cases, sudden cardiac arrest or death

Symptoms are typically triggered by factors that increase sympathetic tone, such as exercise, stress, or certain medications.

Diagnosis

Electrocardiogram (ECG)

• Characteristic findings:
  • Short PR interval (<120 ms)
  • Delta wave (slurred upstroke of the QRS complex)
  • Wide QRS complex (>120 ms)
• During tachycardia, the ECG may show:
  • Narrow complex tachycardia (AVRT)
  • Wide complex tachycardia (atrial fibrillation with rapid ventricular response)

Additional Diagnostic Tests

• Ambulatory ECG (Holter or event monitoring) to capture symptomatic episodes
• Exercise stress testing to provoke tachyarrhythmias
• Electrophysiological study (EPS) to confirm the presence and location of the accessory pathway
• Echocardiogram to evaluate for structural heart disease

Management

Acute Management of Tachyarrhythmias

• Vagal maneuvers (e.g., Valsalva, carotid sinus massage) to terminate the arrhythmia
• Intravenous antiarrhythmic medications (e.g., adenosine, amiodarone) for refractory cases
• Direct current cardioversion for hemodynamically unstable patients

Long-Term Management

• Antiarrhythmic medications (e.g., beta-blockers, calcium channel blockers, flecainide) to prevent recurrent tachyarrhythmias
• Radiofrequency catheter ablation to permanently eliminate the accessory pathway
  • Considered the definitive treatment for symptomatic patients
  • High success rate (>95%) and low complication risk
• Lifelong follow-up and monitoring for recurrence or development of new accessory pathways

The management approach should be tailored to the individual patient's risk profile and symptom severity.

Prognosis

Asymptomatic Patients

• Majority of patients with WPW remain asymptomatic throughout their lives
• Risk of sudden cardiac death is low (estimated at 0.1-0.4% per year)
• Appropriate monitoring and lifestyle modifications are recommended

Symptomatic Patients

• Without treatment, the risk of sudden cardiac death is significantly higher (estimated at 0.6-4% per year)
• Appropriate management, including antiarrhythmic medications or catheter ablation, can significantly reduce this risk
• Excellent long-term outcomes with successful catheter ablation (recurrence rate <5%)

Early recognition and prompt initiation of appropriate management are crucial for optimizing the prognosis in pediatric patients with WPW syndrome.

Further Reading

• Wolff-Parkinson-White Syndrome: 2019 Update on Diagnosis and Management
• 2018 AHA/ACC/HRS Guideline on the Evaluation and Management of Patients with Bradycardia and Cardiac Conduction Delay
• UpToDate: Wolff-Parkinson-White Syndrome in Children
• Wolff-Parkinson-White Syndrome in Children: Noninvasive Diagnosis and Risk Stratification