Current Environment:

What is long QT syndrome?

Long QT Syndrome (LQTS) is an inherited condition that affects the heart’s electrical rhythm and can cause fast, erratic heartbeats. It is named for the prolonged QT interval it causes on an electrocardiogram (ECK or EKG).

Left untreated, LQTS can be a life-threatening condition that can lead to sudden cardiac death. LQTS causes approximately 3,000 to 4,000 sudden deaths of children and young adults each year in the United States.

LQTS is fairly rare. It is estimated that about 1 in every 2,500 children born have the condition.

What are the types of long QT syndrome?

There are three types of LQTS:

  • LQT1 is more likely to cause symptoms with exercise or emotional stress.
  • LQT2 is more likely to cause symptoms with emotional stress.
  • LQT3 is more likely to cause symptoms during periods of rest or sleep.

Long QT Syndrome | Symptoms & Causes

What are the symptoms of long QT syndrome?

Some children with LQTS have no symptoms. This makes family screening particularly important.

Symptoms of LQTS can include:

  • fast heart beat (palpitations)
  • fainting (syncope) during periods of strenuous exercise or emotional distress
  • seizures
  • cardiac arrest

What are the causes of long QT syndrome?

In many cases, LQTS is caused by an inherited genetic mutation passed down from a family member. Children with a parent or sibling who has LQTS have a 50 percent chance of having it as well.

In some cases, LQTS may also be caused by certain medications.

Long QT Syndrome | Diagnosis & Treatments

How is long QT syndrome diagnosed?

Diagnosis of long QT syndrome (LQTS) can be difficult, as many children don’t have symptoms. If your doctor suspects your child has LQTS, he or she may suggest testing. Tests may include:

What are the treatment options for long QT syndrome?

Treatments for LQTS range from lifestyle changes to surgery. The type of treatment your child’s doctor recommends will be based on his or her individual condition.

Lifestyle treatments

Lifestyle changes may include:

  • reducing stress, caffeine, or alcohol, which can provoke arrhythmias
  • changes in diet
  • staying hydrated to maintain electrolytes (sodium and potassium) before, during, and after activities
  • restricting some exercise or competitive sports


Your child’s doctor may prescribe beta-blockers or other types of medications to reduce arrhythmias and risk for sudden cardiac arrest.


Some children with LQTS may need surgery. Options may include:

  • Ablation: This surgical procedure eliminates extra or abnormal electrical pathways within the heart that can cause fast or irregular heart rhythms.
  • Pacemaker: This electronic device is placed surgically inside the body to regulate the heartbeat.
  • Implantable cardioverter-defibrillator (ICD): This small device, similar to a pacemaker, is implanted under the skin, often in the shoulder area. An ICD senses heart rate and, if it exceeds a certain rate, delivers a small, electrical shock that slows the heart down. Some ICDs are combined with a pacemaker to deliver electrical signals to interrupt arrhythmias.

How we care for long QT syndrome

Early diagnosis of LQTS is important. The Center for Cardiovascular Genetics at Boston Children’s Hospital specializes in family based services for children with inherited arrhythmias like long QT syndrome. The program meets with and assesses entire families all at once, usually in one day. Our specialists use genetic testing to identify all family members at risk of developing the condition.

Long QT Syndrome | Programs & Services