The pediatric electrocardiogram Part II: Dysrhythmias

doi:10.1016/j.ajem.2007.07.034

The American Journal of Emergency Medicine

Volume 26, Issue 3, March 2008, Pages 348-358

https://doi.org/10.1016/j.ajem.2007.07.034 Get rights and content

Abstract

The following article in this series will describe common arrhythmias seen in the pediatric population. Their definitions and clinical presentations along with electrocardiogram (ECG) examples will be presented. In addition, ECG changes seen in acute toxic ingestions commonly seen in children will be described, even if such ingestions do not produce arrhythmias per se. Disturbances of rhythm seen frequently in patients with unrepaired and corrected congenital heart disease will be more fully discussed in the third article of this series. Numerous classification schemes for arrhythmias exist; in this article arrhythmias will be grouped based upon their major ECG manifestations.

Introduction

The following article in this series will describe common arrhythmias seen in the pediatric population. Their definitions and clinical presentations along with ECG examples will be presented. In addition, ECG changes seen in acute toxic ingestions commonly seen in children will be described, even if such ingestions do not produce arrhythmias per se. Disturbances of rhythm seen frequently in patients with unrepaired and corrected congenital heart disease will be more fully discussed in the third article of this series. Numerous classification schemes for arrhythmias exist; in this article arrhythmias will be grouped based upon their major ECG manifestations.

Section snippets

Bradyarrhythmias

Bradyarrhythmias are uncommon causes of ECG abnormalities in children without congenital heart disease; they are seen frequently in patients with congenital heart disease who have undergone surgical manipulation of the atria (eg, Fontan procedure, atrial septal defect repair, atrioventricular [AV] canal repair, and older “atrial switch” operations for transposition of the great arteries). Sinus bradycardia is defined by the presence of a sinus rhythm that is abnormal only in that it is slower

Atrioventricular block

The generic term AV block implies a disturbance of impulse conduction from the atria to the ventricles. The anatomic locations of such disturbances vary depending on the underlying mechanism of the arrhythmia. Generally, AV block is categorized into first-degree (1°), second-degree (2°), and third-degree (3°) subtypes. First-degree block (Fig. 2) is identified electrocardiographically by a prolonged PR interval for age. The reader is referred to age-related pediatric norms as discussed in Part

Normal QRS duration tachycardias

Numerous schemes exist for classifying tachycardias; a useful and simple way is to categorize them based upon the QRS duration. In general, tachycardias with a normal QRS duration for age can be considered as originating superior to the AV node, whereas tachycardias associated with QRS prolongation typically originate at locations inferior to the AV node. This scheme is not perfect but allows for ease of organization.

Sinus tachycardia is usually simple to recognize on the ECG (Fig. 8). For the

Abnormal QRS duration tachycardias

Tachycardias demonstrating prolonged QRS duration for age imply a ventricular origin to the arrhythmia. Ventricular arrhythmias also demonstrate “bizarre” QRS morphologies. Ventricular arrhythmias are uncommon in children and usually arise in the setting of severe electrolyte disarray, ingestion, or rare inherited disorders of cardiac conduction. Ventricular arrhythmias, however, are poorly tolerated hemodynamically so prompt recognition and initiation of therapy are vital.

Premature ventricular

Ventricular preexcitation syndromes

The term preexcitation refers to ventricular depolarization that is earlier than expected. Preexcitation can occur via either a reentry pathway or an accessory pathway [18]. In either case, the potential for sustained and dangerous tachycardia exists because the AV node no longer “protects” the ventricles from excessively high atrial rates. The electrocardiographic appearance of preexcitation (Fig. 15) consists of (a) normal P-wave morphology and axis, (b) shortened PR interval, (c) prolonged

Tachycardias associated with a prolonged QT interval

Evaluation of the QT interval is an essential aspect of ECG interpretation. Norms for the corrected QT interval have been published and were discussed in the previous article of this series. Prolongation of the QT interval is often asymptomatic but puts the patient at risk of ventricular arrhythmias, the most common of which is torsades de pointes. Torsades de pointes is a form of polymorphic ventricular tachycardia that has the ECG appearance of “twisting along a string.” Prolongation of the

Toxicology

Children frequently present to EDs after ingestion of medications or other toxins, unintentionally or otherwise. Obtaining an ECG is an important aspect of evaluating these patients. A number of agents cause QRS prolongation, mainly via blockade of the sodium channels responsible for depolarization during phase 0 of the myocardial action potential. Examples of such agents include tricyclic antidepressants, diphenhydramine, propanolol, hydroxychloroquine, and many antiarrhythmic agents [22]. QRS

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DiagnosticsThe pediatric electrocardiogram Part II: Dysrhythmias