Focus on Diagnosis: Cardiac Arrhythmias in Children

Abstract

1. Eric A. Biondi, MD* 1. *Resident in Pediatrics, University of Rochester Medical Center, Rochester, NY. Although most childhood arrhythmias are benign, prompt and correct diagnosis of a serious rhythm disturbance in a child can be lifesaving. Such rhythm disturbances may arise at any age and have a wide variety of presentations. This article discusses various pediatric arrhythmias that may be encountered by the community pediatrician, highlighting their presentation, findings on electrocardiography (ECG), and when to refer for additional evaluation. ### Sinus Rhythm and Sinus Arrhythmia Some rhythm disturbances originate within the sinoatrial (SA) node. This cardiac pacemaker is located in the upper wall of the right atrium and initiates electrical conduction through the cardiac muscle. The term sinus rhythm designates normal heart rhythm controlled by this node. ECG shows a P wave with a leftward and inferior axis before each QRS complex and a normal PR interval (120 to 200 msec). Sinus arrhythmia occurs in healthy children and is described as a decrease in SA node firing subsequent to activation of the vagus nerve by exhalation. The heart rate, thus, varies with respiration, and ECG shows sinus rhythm with a prolongation of the R-R interval during exhalation. Such prolongation may be suppressed with exercise or other causes of sinus tachycardia. This finding is normal and is not a reason for referral. ### Sick Sinus Syndrome Although most significant arrhythmias occur below the SA node, one emanating from the SA node, sick sinus syndrome (SSS), is worth mentioning briefly. This rhythm is a result of SA nodal dysfunction and is seen most often in patients who had prior cardiac (especially extensive atrial) surgery or cardiomyopathy. Although many forms of SSS are asymptomatic, common clinical manifestations include shortness of breath, chest pain, and syncope. The rhythm is characterized by …