What is Atrioventricular Reentrant Tachycardia (AVRT)?

Supraventricular tachycardia or SVT is a type of heart racing where the heart beats abnormally fast. In SVT, the abnormal rhythm of the cells above the ventricles (supraventricular) are a part of the abnormal circuit that causes the fast heart rate (tachycardia).

Atrioventricular Reentrant Tachycardia or AVRT is one of the types of SVT. AVRT involves both the atria and the ventricles (atrioventricular). There is an extra electrical connection, called an “accessory pathway” between the upper and lower chambers of the heart that allows the electrical impulses to conduct in a continuous abnormal loop (reentrant) causing a fast heart rate. During an episode of AVRT, the heartbeat is not controlled by the sinus node, where normal electrical conduction starts. 

It is the most common type of heart racing in children and adolescents. In most cases, children with SVT have structurally normal hearts, but SVT can also occur with certain congenital heart defects.

Effects and Symptoms

The most common symptom is the feeling of heart racing, felt as palpitations. SVT usually feels different from the normal rapid heart rate felt during exercise. SVT may be accompanied by dizziness, difficulty breathing, chest pain or fainting. Most people will feel tired or fatigued during an episode of SVT.

SVT can be dangerous if the episodes are very long. The acceptable duration of episodes should be discussed with your physician. It can also be dangerous if it causes fainting. Most people with SVT do not faint.

Diagnosis

Doctors can become suspicious of SVT because of the character of a child’s symptoms. It can be challenging to determine whether palpitations are due to SVT or if it were because of normal heart rhythm because several things can normally cause fast heart rates such as exercise and emotion. Other medical conditions can also affect the heart and cause it to beat inappropriately fast. SVT is confirmed by recording the heart rhythm on an ECG during an episode of palpitations.

Management and Treatment

SVT episodes are not life-threatening but they should be treated and prevented, if possible. If SVT occurs frequently and interferes with normal activities, there are several options for treatment. You will need to discuss with your physician which of these treatment options is appropriate for you:

1. Medications:  Several medications are available that can help reduce the number of episodes of SVT.  If you arrive at a hospital in SVT, they may start an intravenous line and give medication to try to stop the heart racing. 
2. Radiofrequency Catheter Ablation:  This procedure is done in the heart catheterization lab and delivers energy in a very specific way to destroy (“ablate”) the abnormal cells or pathway causing your SVT.
3. Not treating SVT is an option if the episodes are infrequent, don’t last very long, and cause few symptoms.