To understand abnormal heart rhythms, or heartbeats, it can be helpful to first understand how your heart’s electrical system governs the heartbeat.

The Heart's Electrical System

Over the course of your life so far, you were most likely familiar with the heart because of its beating. Perhaps you heard your heartbeat through a stethoscope or listened to someone else's heartbeat. Or maybe you put two fingers to your wrist or neck to feel your pulse. Your pulse is your heartbeat sensed in your arteries.

Your heartbeat is the relaxing and contracting of your heart's chambers:

• The upper chambers of the heart are called the atria.
• The lower chambers of the heart are called the ventricles.

This relaxing and contracting of the heart is stimulated by electrical impulses that travel through your heart and regulate your heartbeat. The electrical impulse begins in the sinoatrial (SA) node in the top of the right chamber (atrium) of the heart. The electrical impulse travels through the muscles of both atria. The atria contract (squeeze) in response.

The electrical impulse is then picked up by the atrioventricular (AV) node, which is located between the atria and the ventricles. It is then passed to the fibers of the His-Purkinje system. The ventricles fill with blood from the atria before the electrical impulse causes them to contract. Once the ventricles contract, they force the blood out of the heart and to the lungs and the body.

The timing of the flow of blood through the heart is key for good health. Problems with the heart's electrical system can be life threatening. If there is a problem with the heart’s electrical system, the patient's care team may recommend implantation of a pacemaker or other treatment.

Abnormal Heart Rhythms

An abnormal heart rhythm (or heartbeat) is called an arrhythmia or dysrhythmia. The number of heartbeats in a minute determines the heart rate. Normal heart rates change as a child matures.

• The heart of a newborn baby normally beats about 140 times per minute.
• A five-year-old may have a heart rate of 100 beats a minute.
• The normal heart rate of an older child or teenager at rest is about 70 beats a minute.

A person’s heart rate changes easily. During exercise, it beats faster. During rest, it slows.

Usually the heart beats at regular intervals. Arrhythmia (or dysrhythmia) occurs when the heart beats irregularly. One type of arrhythmia, called sinus arrhythmia, is normal. It occurs when a child breathes in and the heartbeat increases and when he or she breathes out and the heart rate slows.

If your child’s doctor detects an abnormal kind of arrhythmia, he or she may recommend tests and/or a visit to a pediatric cardiologist (a doctor with special medical training in children's heart problems).

Often an irregular heartbeat has no symptoms and goes unnoticed by parents and the child. Sometimes it is detected during a routine wellness exam.

Medications – those that are prescribed and those bought without prescription at your pharmacy – may contribute to your child’s irregular heartbeat. It is important to talk with your doctor about your child’s medications if an irregular heartbeat is detected.

You can read more about common arrhythmias in children here.