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45 Arrhythmias

Although infrequent in the pediatric population, arrhythmias represent potentially significant causes of morbidity and mortality. The diagnosis and management of arrhythmias require an understanding of age-dependent normal variations in heart rate (Table 45-1). This chapter describes the etiology, clinical significance, and treatment options of common arrhythmias found in infants, children, and adolescents, including bradyarrhythmias, tachyarrhythmias, and rhythm disturbances leading to syncope and sudden death.

Table 45-1 Normal Heart Rate for Age

Age Heart Rate (beats/min)
Newborn 110-160
1-6 months 100-180
6-12 months 95-170
1-3 years 95-150
3-5 years 70-130
5-8 years 65-120
8-12 years 65-120
12-16 years 60-110
>16 years 60-100

Sinus Arrhythmias and Premature Impulses


Primary causes of symptomatic bradyarrhythmias in the pediatric population include sinus node dysfunction and atrioventricular (AV) block. A wide spectrum of clinical presentations can occur. Infants may present with poor feeding, lethargy, or seizures, and older children can have lightheadedness, fatigue, exercise intolerance, or syncope. Severe bradycardia can present with signs of poor perfusion and shock and can lead to death. A complete evaluation of each patient’s clinical history is needed to exclude underlying medical conditions that may lead to symptomatic bradyarrhythmias.

Atrioventricular Conduction Abnormalities

Abnormal AV conduction occurs when transmission of the normal sinus node impulses is delayed or blocked because of an abnormality in the conduction system, specifically the AV node or His-Purkinje system (Figure 45-1).

First-Degree Atrioventricular Block

Because of an abnormal delay in conduction through the AV node, first-degree AV block results in prolongation of the PR interval above the upper limits of normal for age and heart rate (Figure 45-2). It is important to note that bradycardia does not occur because of first-degree AV block alone. This type of block can appear in otherwise healthy children as a benign phenomenon, usually related to increased vagal tone. Other causes may include cardiac surgery, rheumatic fever, Lyme disease, digoxin toxicity, and electrolyte imbalance. Isolated first-degree AV block does not require treatment unless there is progression to more advanced AV block.

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