Chapter 46: Common Dysrhythmias

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.

Wolff-Parkinson-White Syndrome

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 ...