Supraventricular Tachycardia (SVT)

Supraventricular tachycardia (SVT) is an abnormally fast heart rhythm or heartbeat caused by a disruption to the heart’s electrical system. It is the most common arrhythmia or irregular heartbeat diagnosed in children.

Many children are born with the condition or it develops later in life. Other times, SVT develops because of other heart conditions. Many times, infants born with SVT will outgrow the disorder but it can also be a lifelong problem for many people.

What happens in SVT?

The heart consists of four chambers. The top chambers are known as the atria while the lower chambers are called the ventricles. SVT occurs when a child’s heartbeat does not follow the regular pathway from the atria to the ventricles due to a heart defect or other condition. This happens when an abnormal electrical pathway exits in the heart and forms a “short circuit.” The short circuit bypasses the normal electrical pathway which causes the heart’s rhythm to beat very rapidly. When the normal pathway is disrupted, the heart must work harder to do its job.

Children may experience a fast heartbeat suddenly, and it may last a few minutes to many hours. When a rapid heart rate occurs from time to time it is called paroxysmal supraventricular tachycardia (PSVT). When a reaction to stress or other activities causes an irregular heartbeat, this fast heartbeat is called sinus tachycardia.The longer tachycardia occurs, the more tired the heart becomes, which impacts blood flow throughout the body. Although SVT is not typically life-threatening, it can cause discomfort, fatigue, dizziness, and shortness of breath.

A normal heart rate for an infant is 100 to 160 beats per minute while a normal heart rate for children and adults is 60 to 100 beats per minute. While a high heart rate in children is often the cause of physical activity or illness, a dangerously high heart rate in children (faster than these normal resting heart rates) or tachycardia should be evaluated at a hospital by a pediatric cardiologist.

Symptoms of SVT

Refer to pediatric cardiology if your infant, toddler, or child experiences any of the following tachycardia symptoms causing a fast heart rate. The most common symptom is heart palpitations, a fast or pounding heartbeat in your child’s chest.

Chest pain or discomfort
Racing or pounding heart
Feeling lightheaded or dizzy
Weakness or tiredness
Shortness of breath

Diagnosis of Supraventricular Tachycardia

At Riley Children’s Health, a pediatric cardiologist will evaluate your child for heart rhythm concerns. Our pediatric cardiologists use various tests to diagnosis SVT including electrocardiogram (ECG/EKG), Holter monitor and event monitor.

An ECG/EKG records the electrical signals in the heart and it provides results as soon as the test is done. A Holter or event monitor is a portable device that records heart activity over an extended period. A Holter Monitor is an ECG/EKG test recorded for 24 or more hours and includes recordings of your child’s heart while at home. An event monitor can be worn for up to 30 days and it records heart activity when your child experiences symptoms. A push of a button records symptoms in real time.

Treatments

Many irregular heartbeats do not need treatment because the problem may resolve on its own. Treatment for SVT may only be needed if it the symptoms persist or last a long time. If so, our pediatric cardiology team may suggest:

Medicine. SVT medications such as beta blockers may be recommended to slow your child’s heart rate. Other medications include Digoxin, sodium channel-blockers, or calcium channel-blockers with the same goal to lower the chance of frequent or long episodes of SVT.

Catheter ablation. Catheter ablation is a highly successful procedure that can permanently restore the heart’s normal rhythm. During this procedure, your child is asleep and a flexible, plastic tube is guided into the heart chambers to detect the abnormal electrical pathway with the catheter’s electrodes or sensors. Once the abnormal pathway is found, a different catheter is used to eliminate the abnormal electrical pathway responsible for SVT.

Catheter ablation traditionally uses X-ray guidance to position the catheter. At Riley Children’s, we have pediatric cardiologists that specialize in heart rhythm disorders. These specialists use advanced techniques and computerized 3D mapping of the heart, which allows patients to have catheter ablations with zero or nearly-zero exposure to X-ray and radiation.

Key Points to Remember

Supraventricular tachycardia (SVT) is an abnormally fast heart rhythm or heartbeat caused by a disruption to the heart’s electrical system. A pediatric cardiologist should evaluate any irregular heartbeat.
SVT is caused by an electrical disruption in the heart.
Although generally not life-threatening, SVT may cause chest discomfort, a racing heart, dizziness, and in rare cases, people may lose consciousness.
Infants with SVT often outgrow the disorder, but persistent problems can require medications or catheter ablation.

Support Services & Resources

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Centers for Disease Control and Prevention

This U.S. government website includes resources to educate parents and caregivers of children with congenital heart disease. It also shares information for the growing population of adults who are living with congenital heart disease.

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