What types of abnormal slow heart rhythms develop in children?

Mark Sklansky, MD
Pediatric Cardiology
Most children with slow heart rates have normal hearts that have been trained/conditioned over time by exercise. Some children (and even newborns) may develop slow heart rates because of cardiac pathology (such as long QT syndrome, heart block or sick sinus syndrome). Some of these children may require implantation of permanent pacemakers. While some children develop slow heart rhythms after heart surgery, others may develop (or be born with) slow heart rhythms unrelated to congenital heart disease or heart surgery.

Some abnormal heart rhythms, or arrhythmias, are fast, others are slow, and some are irregular. A number of slow arrhythmias may develop in children and young adults. You may hear slow heart rhythms described with the term bradycardia.

Atrioventricular (AV) block occurs when some or all of the natural electrical signals that govern your heartbeat by traveling from the heart's upper chambers (atria) to the lower chambers (ventricles) are impaired or fail to transmit. AV block is also often called heart block. In this condition, the atria may contract at a normal rate, but the signals to the ventricles are “blocked.”

There are various types of AV block, depending on the mechanism of block. For example, second-degree AV block occurs when the electrical impulse from the atria occasionally does not pass through to the ventricles. In “complete AV block,” none of the normal electrical impulses from the atria pass through the atrioventricular node, leaving the ventricles to generate their own native rhythm, which is typically slower than the normal sinus rhythm. In babies born with complete AV block, this may be associated with long QT syndrome or maternal lupus.

Sinus arrhythmia, despite its name, is not a true arrhythmia. It represents an exaggeration of the normal variation of heart rate that occurs during inspiration (breathing in) and expiration (breathing out). It does not mean that a child will be prone to other true arrhythmias later in life.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.