Some children are born with an abnormally rapid heartbeat due to a disruption in the heart’s electrical system, a condition known as supraventricular tachycardia (SVT). SVT can occur in utero, shortly after birth and through adulthood.
In infants, the heart rate can be as fast as 300 beats per minute and older children it is often as fast as 220 to 250 beats per minute. According to medical resources, normal heart rate for an infant between 1 and 11 months old is 80 to 160 beats per minute. For adults and children over 10 years of age, a normal rate is 60 to 100 beats per minute.
The heart has four chambers, two on top, and two below. The upper chambers are known as atria, and the lower chambers are called the ventricles.
The human heart comes with a built-in pacemaker located in the right atrium known as the sinus node. It sends an electrical impulse throughout the atria, which results in atrial contraction. This impulse is received by another node called the atrioventricular (AV) node.
The AV node has the important job of delaying the impulse just long enough to ensure the atria have fully contracted and squeezed blood down to the ventricles. From there, the electrical current travels down to the ventricles, causing them to contract and pump blood to the lungs and body.
The most common forms of Supraventricular Tachycardia (SVT) in children are caused by extra electrical connections. One such disorder is Wolff-Parkinson-White syndrome, a disorder that causes SVT due to an extra electrical pathway between the top and bottom chambers of the heart.
SVT is generally not a life-threatening disease, but it can be very uncomfortable. Any irregular heartbeat should be evaluated by a physician.
In some patients, rapid heart rate may last for minutes or even longer. You should consult a physician if you notice any of the following symptoms:
SVT can be fleeting, and it is possible for symptoms to go unnoticed.
A doctor typically diagnoses this condition by recording the heart’s electrical activity. Electrocardiograms, Holter monitors and event monitors are the most common methods for recording the heart’s electrical activity and diagnosing SVT. Holter monitors and event monitors are portable devices that can record the heart’s activity for extended periods. Exercise stress tests are sometimes used to help diagnose SVT.
Fortunately, many cases of irregular heartbeat require no treatment at all because the problem may resolve on its own. Other cases are treatable with medications that target the AV node. The most commonly-used medicines are beta blockers. Other medicines including Digoxin and calcium channel-blockers are also useful.
Occasionally, more persistent problems may prevent the heart from pumping the necessary amount of blood to the brain or body. In this event, a catheter ablation may help restore the heart’s normal rhythm.
Catheter ablation inserts a flexible, plastic tube into the heart chambers through a blood vessel in the groin, neck or arm. The catheter has electrodes, which are sensors that allow doctors to see electrical activity and diagnose problems within the heart. Once a diagnosis is made, a separate catheter localizes and eliminates the abnormal electrical pathway responsible for SVT.
Catheter ablation traditionally uses x-ray guidance (fluoroscopy) to position the catheter. Riley at IU Health cardiologists specialize in heart rhythm disorders. We use advanced techniques and computerized three-dimensional mapping of the heart, which allows some patients to have catheter ablations with zero or nearly-zero exposure to radiation.
Visit these resources to find support groups and services, and learn more about supraventricular tachycardia.
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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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