Heart and Blood Conditions


What Is Arrhythmia?

Arrhythmia (pronounced a-RITH-me-ah) is an abnormal heartbeat. Typically this means a child's heart is beating too fast or too slow for the activity they are doing. In some children an abnormal heartbeat causes symptoms. But in many cases, it causes no problem.

The heart has four chambers that work like a pump. The atria are the two top chambers. They receive blood from the lungs and the rest of the body. The ventricles are the two bottom chambers. They pump blood out to the lungs and the rest of the body. It is important for all four chambers of the heart to work in sequence with one another to create an effective pump.

The sinus node is located at the top of the right atrium. This node is known as the "pacemaker" of the heart. It works to control the normal heart rate. It makes the heart beat slower during times of rest or sleep and beat faster with exercise or when you are scared or excited.

Each heartbeat begins with an electrical wave (signal) that passes from the sinus node through the atria. This signal travels through the atria much like the ripples created in water when a pebble is thrown in. This electrical signal makes the atria contract, or squeeze, making them beat.

Next, the electrical signal moves from the atria into the junction between the atria and ventricles. This junction is known as the atrioventricular node (AV node). The AV node delays the signal slightly, and then passes it on to the ventricles, making them beat.

After the ventricles beat, the heartbeat cycle is complete. There should be no way for the electrical signal to travel backwards up to the atria. Rather, the next heartbeat starts in the sinus node and follows the same path.

Electrical abnormalities of the heart are the underlying cause of an arrhythmia. These abnormalities can lead to a heartbeat that's too fast (tachycardia, pronounced tack-ih-CARD-ee-ah) or too slow (bradycardia, pronounced brad-ih-CARD-ee-ah).

Arrhythmia in Children

There are many kinds of arrhythmia that affect different chambers of the heart in different ways. Some are harmless, and some are serious. Children with signs or symptoms of arrhythmia should be evaluated by a cardiologist.

There are also many causes of arrhythmia. Some may be present at birth, and others are acquired, such as after an infection of the heart or heart surgery.

Supraventricular tachycardia (SVT) and long Q-T syndrome (LQTS) are examples of arrhythmias that a child may be born with. SVT is the most common cause of a fast heartbeat and is usually not life threatening. LQTS, however, can be linked with life-threatening arrhythmias triggered by exercise, startle or fright.

After heart surgery, the normal electrical system of the heart may become scarred and not function normally. It may cause very rapid heartbeats or, more commonly, a heartbeat that's too slow for the child's level of activity.

Arrhythmia at Seattle Children's

We have extensive experience providing the treatment these patients may require through our Arrhythmia Program , including radiofrequency ablation , pacemaker , defibrillator implantation, and surgery . We also have a pediatric cardiac anesthesia team and a  cardiac intensive care unit  ready to care for children who undergo heart surgery.

When you come to Children's, a team of people will take care of your child. Along with your child's cardiologist, you are connected with neonatologists, nurses, child life specialists, social workers and others, if their expertise is needed. We work together to meet all of your child's health needs and help your family through this experience.

Since 1907, Children's has been treating children only. Our team members are trained in their fields and also in meeting the unique needs of children. For example, the doctors who give your child anesthesia are board certified in pediatric anesthesiology. This means they have extra years of training in how to take care of kids. Our child life specialists know how to help children understand their illnesses and treatments in ways that make sense for their age. Our expertise in pediatrics truly makes a difference for our patients and families.