Heart and Blood Conditions

Long QT Syndrome

What is long QT syndrome?

Long QT syndrome (LQTS) is a disorder of the heart’s electrical rhythm that can cause fast and irregular heartbeats (arrhythmia). It can be present at birth, but may not be detected until later in life. LQTS is rare and affects children and young adults.

There are 4 chambers in the heart: the top 2 are the atria and the lower 2 are the ventricles. The heart uses a complex electrical system to make the muscle walls of the atria and ventricles work together to pump blood.

A heartbeat is the squeezing and relaxing of the muscle walls at the right times and in the right order. The heartbeat starts in the right atrium. When a group of cells called the sinus node sends an electrical signal, the heartbeat is initiated. This is known as the heart’s pacemaker.

The signal travels on nerve-like fibers from the atria to the ventricles and causes the muscle to squeeze at the right time. The muscle then relaxes so that it is ready for the next beat. In children with LQTS, the relaxation phase takes longer than normal, making the heartbeat more likely to be fast and irregular.

Children with LQTS can suddenly develop a fast heartbeat that keeps their heart from squeezing the way it should. This can be more common if they are doing a strenuous activity, are excited or are startled.

Fast and irregular heartbeats can prevent the body and brain from getting as much oxygen-rich (red) blood as normal. If someone’s brain doesn’t get enough oxygen, they can faint and could die without warning.

Long QT Syndrome at Seattle Children’s

Our heart team has treated many children and young adults with LQTS. We have extensive experience with the treatment these patients may require.

When you come to Seattle Children’s, a team of people will take care of your child. Along with your child’s heart doctor (cardiologist), you are connected with heart rhythm specialists, 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.

Seattle Children’s has been treating children since 1907. Our team members are trained in their fields and 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.

Long QT Syndrome in Children

Some children are born with LQTS because one or both of their parents passed down a gene that causes the condition. This is known as “inherited LQTS.” Parents may not know they have the gene and LQTS themselves because many people with LQTS have no symptoms. There are at least 12 genes that have been associated with LQTS.

Some children and young adults get LQTS because they take medicines that make the relaxation phase of the heartbeat longer than normal. This is caused “acquired LQTS.”

LQTS is rare; about 1 in every 7,000 people has it.