Pediatric Long QT Syndrome

What Causes Long QT Syndrome in Children?

Most children with long QT syndrome inherit a gene change (mutation/variant) from a parent that causes problems with their heart’s ion channels. These channels are tiny pores on the surface of each heart muscle cell. They open and close to move electrically charged calcium, potassium and sodium atoms (ions) in and out of each cell. It’s these actions that generate the heart’s electrical activity. 

Researchers have identified variants in at least 15 genes that may cause inherited LQTS. A gene change may cause a child to have too few ion channels, or the ion channels may not work as they should. Rarely, the gene change affects a child with no family history of LQTS. This is a sporadic or de novo gene mutation.

What Are the Types of Inherited LQTS in Children?

Healthcare providers determine the type of inherited LQTS based on the genetic mutation and/or the ion channel change that causes the condition. The three most common LQTS types include:

• LQT1: The heart’s potassium ion channels don’t work as they should. This is the most common type of LQTS. 
• LQT2: The heart doesn’t have enough potassium ion channels at the cells’ surface.
• LQT3: The heart’s sodium ion channels don’t work as they should.

Acquired Long QT Interval in Children 

A small number of children develop an acquired long QT interval even when they don’t have an underlying genetic change. Taking certain medications, eating disorders or electrolyte imbalances from severe diarrhea and/or vomiting can cause an acquired long QT interval. 

A child’s heart may develop an abnormal heart rhythm (cardiac arrhythmia) during this time. However, long QT intervals can go away once providers treat the underlying cause. This type differs from inherited LQTS, which is a lifelong genetic condition.

What Are the Signs and Symptoms of Pediatric Long QT Syndrome? 

Signs of LQTS typically appear during the pre-teen and teen years, but may occur at any time. The symptoms may come on or worsen during physical activity, emotional excitement, stress, sleep or right after waking. 

LQTS symptoms include:

• Fainting (syncope)
• Gasping for breath while sleeping 
• Heart palpitations, especially right before fainting
• Near-drowning incident (or drowning) due to fainting while swimming
• Seizures

What Are the Complications of Pediatric Long QT Syndrome? 

LQTS causes ventricular tachycardia (VT or V-tach). This abnormal heart rhythm or arrhythmia occurs when the heart’s lower chambers beat too fast. Most children have a resting heart rate between 60 to 120 beats per minute. With VT, the heart rate is typically more than 200 beats per minute.

Children with LQTS are more likely to develop a severe type of VT called Torsades de Pointes, which causes an extremely rapid and abnormal heart rhythm. All types of VT increase a child’s risk of sudden cardiac arrest. 

Because of these complications, it’s important for your family and others who care for your child to know how to use an automated external defibrillator (AED). These life-saving portable devices deliver an electric shock to the heart, helping to restore a normal heartbeat when someone experiences cardiac arrest from a rapid arrhythmia.

How Is Pediatric Long QT Syndrome Diagnosed?

Pediatric electrophysiologists and cardiac genetic experts at Lurie Children’s work together to diagnose LQTS in children. An electrophysiologist is a heart doctor who specializes in heart rhythm problems. This doctor will perform a physical examination, review your child’s symptoms and medical history, and review your family’s medical history. 

Diagnostic tests for LQTS include:

• EKG/ECG to measure the QT interval
• Holter and event monitoring to record heart electrical activity for more than 24 hours
• Cardiac stress test to see how your child’s heart responds to physical activity and stress
• Genetic testing to look for gene mutations known to cause LQTS 

How Is Pediatric Long QT Syndrome Treated?

Currently, there isn’t a cure for inherited LQTS. However, treatments can help keep the heart in its normal rhythm, lowering your child’s risk of life-threatening complications. With proper treatment, many children with LQTS lead full, active lives. Specialists at the Heart Center at Lurie Children’s have deep expertise in caring for children with LQTS.

Treatments vary depending on the type of LQTS and your child’s unique symptoms. At Lurie Children’s, your child benefits from comprehensive treatment options.

Medications

Medications help keep the heart beating in a safe rhythm. Your child may need these medications for life. Medications for LQTS include: 

• Beta-blockers to reduce the effects of adrenaline surges on the heart
• Sodium channel blockers to slow the movement of sodium through ion channels, which can shorten the QT interval in certain types of LQTS

Heart Devices 

Some children need an implantable heart device to maintain a healthy heart rhythm. Pediatric electrophysiologists and heart surgeons at Lurie Children’s work together to surgically place these life-saving devices. We offer the latest heart devices, including some that are only available in clinical trials.

Depending on your child’s needs, they may receive:

• Implantable cardioverter defibrillator (ICD): An ICD delivers an electric shock when it detects a dangerous heart rhythm. Some ICDs also work as pacemakers, keeping the heart beating at a steady pace. 
• Pacemaker: This device keeps the heart beating in a safe, steady rhythm. It doesn’t shock the heart like an ICD.

Lifestyle Changes 

Certain lifestyle changes can help protect your child’s heart. Our care team may recommend your child: 

• Drink enough water to prevent dehydration and electrolyte imbalances
• Modify physical activities and take precautions with sports to be as safe as possible
• Find healthy ways to manage stress 
• Lessen exposure to sudden loud noises or excitement
• Minimize the use of medications that adversely affect the heart rhythm

What Is Lurie Children’s Approach to Caring for Children With Long QT Syndrome?

Pediatric specialists at the Heart Center at Lurie Children’s have deep expertise in caring for children with LQTS. We’re home to one of the premier electrophysiology (EP) programs in the nation and the largest in Illinois. 

Your family benefits from:

• Dedicated arrhythmia care team: Our EP team includes highly specialized doctors, trained pediatric arrhythmia nurses, advanced practice providers and cardiac genetic counselors. This team is available 24/7 to manage children and young adults with all types of arrhythmia.
• Specialized genetic services: Specialists at our Cardiovascular Genetics Center help families understand LQTS and the impact the diagnosis may have on future family-planning decisions. We offer genetic counseling and screenings for family members who may have an LQTS gene mutation. 
• Nationally recognized cardiac programs: Your child receives heart services at the nation’s best children’s hospital for pediatric cardiology and cardiac surgery, as recognized by Newsweek. We’re also nationally ranked for our heart services by U.S. News & World Report.
• Comprehensive heart services: Our LQTS care includes arrhythmia management, ongoing heart monitoring, medications, heart devices and more. We partner with your family to manage every aspect of your child’s cardiac care.
• Support for young adults: As your child gets older, we work closely with care teams at the Bluhm Cardiovascular Institute at Northwestern Memorial Hospital to ease their transition to adult care. 
• Research and clinical trials: Experts at our Center for Cardiovascular Innovation (CCI) are active in national research and clinical trials to find new ways to diagnose and treat pediatric heart diseases. Your child may benefit from promising new therapies still in development.

The Heart Center at Lurie Children’s 

Doctors at the Heart Center at Lurie Children’s are nationally recognized for their expertise in managing complex heart conditions in infants, children, teens and young adults. Our experienced team of pediatric electrophysiologists has deep expertise in diagnosing and treating children with the most complex heart rhythm issues. We partner with your family to provide compassionate, supportive care through each step of your child’s medical journey. 

Learn more about our Heart Center