The term arrhythmia refers to an abnormal heart rhythm. Normal electrical conduction typically involves transmission of electricity originating in the sinus node in the top right corner of the heart, through the AV node in the middle of the heart, and then down to the ventricles. A number of different arrhythmias may potentially affect the heart of a child.

One of the most common arrhythmias found in children is supraventricular tachycardia. With SVT, there is usually an extra conducting pathway from the atria to the ventricles. The presence of an extra conducting pathway can allow for a circuit to be set up between the extra pathway and the normal AV node. This may result in a much faster than normal heart rate, called supraventricular tachycardia. Wolff-Parkinson-White syndrome, or WPW, is one form of supraventricular tachycardia.

Less common arrhythmias found in children include atrial tachycardia, atrial flutter, and very rarely atrial fibrillation. Ventricular tachycardia may also occur in children, although it is much less common than seen in adults.

Fortunately most arrhythmias in children are treatable with either medication or procedures to eliminate them. A cardiac catheterization, electrophysiology study and radiofrequency ablation may occasionally be necessary.