Three important dysrhythmias in the pediatric population include:

• 
  

  Wolff-Parkinson-White syndrome.

  
  
• 
  

  Long QT syndrome.

  
  
• 
  

  Complete Heart Block.

All three conditions will be covered sequentially in this chapter.

Patient Story

A previously healthy 14-year-old female presents with a 1-month history of rapid onset, rapid offset palpitations without any identifiable precipitating factors. The physical examination is unremarkable. The electrocardiogram (ECG) showed a delta wave, wide QRS, and short PR interval (Figure 46-1).

Introduction

Wolff-Parkinson-White (WPW) syndrome is a congenital abnormality involving the presence of abnormal conduction tissue, or accessory pathway, between the atria and the ventricles in association with supraventricular tachycardia (SVT).¹

Synonym

Pre-excitation or WPW syndrome.

Epidemiology

• 
  

  In large-scale general population studies involving children and adults, the prevalence of WPW is estimated to be 1 to 3 in 1000.²

Etiology and Pathophysiology

• 
  

  Ventricular pre excitation occurs due to electrical conduction down an accessory pathway (AP).

  
  
• 
  

  AP conduction circumvents the usual conduction delay between the atria and ventricles, which occurs at the AV node (AVN), and predisposes the patient to develop reentrant tachycardia.

  
  
• 
  

  The most common type of supraventricular tachycardia seen in patients with WPW is orthodromic reentrant tachycardia (ORT; Figure 46-2).

  
  
• 
  

  Most commonly precipitated by a premature atrial contraction (PAC), the cardiac impulse travels down the AV node to the ventricles and then back to the atria via the accessory pathway.Rarely, antidromic reciprocating tachycardia (ART) occurs due to antegrade conduction down the accessory pathway and retrograde conduction up the AVN.

Risk Factors

• 
  

  Mutations in the PRKAG2 gene can cause familial WPW syndrome.

  
  
• 
  

  Congenital anomalies such as Ebsteins and hypertrophic cardiomyopathy are associated with WPW.

Diagnosis

Clinical Features

• 
  

  Patients with WPW can be asymptomatic.

  
  
• 
  

  The most common clinical manifestation is palpitations.

  
  
• 
  

  Syncope or sudden death is rare and associated with rapid ventricular conduction of atrial fibrillation.

  
  
• 
  

  Physical exam is usually unremarkable. During periods of SVT, tachycardia can be noted with a decrease in blood pressure. If the episode has been untreated for several hours, patients can manifest poor perfusion, hepatomegaly, and cardiac failure.

  
  
• 
  

  Stigmata of associated congenital anomalies such as Ebstein anomaly should be excluded.

Imaging

• 
  

  The ECG will show classic findings of WPW: (1) short PR interval, (2) delta wave, and (3) wide QRS complex.

  
  
• 
  

  In patients with atrial fibrillation and rapid accessory pathway conduction, an ECG will show an irregularly, irregular, wide complex tachycardia (Figure 46-3). This is the cause of sudden death in patients with WPW.

Differential Diagnosis

• 
  

  Other types of arrhythmias (AVNRT, atrial tachycardia, or ventricular tachycardia) are typically excluded by an ECG during the tachycardia.

  
  
• 
  

  Other rare pre-excitation subtypes (Mahain fibers, permanent junctional reciprocating tachycardia) can also be distinguished by ECG findings.

Management

• 
  

  Treatment must be individualized for each patient and should include individual risk assessment.

  
  
• 
  

  Reentrant SVT will terminate with vagal maneuvers (Valsalva or carotid message) or adenosine.

  
  
• 
  

  Two main treatment approaches to WPW syndrome are pharmacotherapy and electrophysiology study (EPS) with catheter ablation.

  
  
  
  
  • 
    

    EPS with catheter ablation is the first-line treatment for symptomatic WPW syndrome.³ SOR A

    
    
  • 
    

    AVN blocking agents (digoxin, calcium channel blockers) are contraindicated in patients with WPW.^3,4 SOR B

Referral

• 
  

  Patients with WPW require an evaluation by a pediatric electrophysiologist.

Prevention and Screening

• 
  

  No preventive modalities currently exist since mostly WPW is congenital in origin.

  
  
• 
  

  No established screening is being currently used in the US.

Prognosis

• 
  

  Once identified and appropriately treated, WPW syndrome has an excellent prognosis.

  
  
• 
  

  Mortality is rare and is related to Sudden Cardiac Death (SCD). Incidence of mortality in SCD in WPW syndrome is found to be 1 in 100 symptomatic patients when followed up to 15 years.⁵

Follow-Up

• 
  

  Regular follow-up is needed to assess for recurrence of arrhythmia, adverse reaction to medicines, and to assess the effectiveness of therapy.

Patient Education

• 
  

  Close follow-up with patients diagnosed with WPW syndrome is essential to assess the need and timing of interventions.

Patient Story

A 12-year-old female presents with recent syncope. She was swimming during a family vacation on a beach. She lost consciousness and was unresponsive for 30 seconds. She does not recall a prodrome prior to the syncopal event. She had started a decongestant medication for Upper respiratory tract infection symptoms the day prior. Her mother and grandmother have also had syncopal events in the past associated with exercise. Her ECG shows QTc prolongation (Figure 46-4).