Atrioventricular nodal reentry tachycardia (AVNRT) is a type of irregular heartbeat, also called an arrhythmia. It is the most common type of supraventricular tachycardia.

People with AVNRT have an irregularly fast heartbeat that often starts and ends suddenly. In AVNRT, the heart beats more than 100 times a minute. The condition is due to a change in heart signaling. There is an extra pathway for heart signals to travel, called a reentrant circuit. That extra pathway causes the heart to beat too early.

AVNRT tends to occur more often in young women. But anyone can have it at any age. AVNRT may not need treatment. When recommended, treatment may include specific actions or movements, medicines, or a heart procedure.

Tests used to diagnose atrioventricular nodal reentry tachycardia (AVNRT) may include:

• Blood tests to see how well the thyroid is working and to check for heart disease or other conditions that may trigger an irregular heartbeat.
• Electrocardiogram (ECG) to check the electrical activity of the heart and look at the heartbeat.
• Holter monitor, a heart monitor that you wear during everyday activities, usually for 1 to 2 days. This monitor can find irregular or fast heartbeats that might not occur during a standard electrocardiogram (ECG).
• Echocardiogram, which uses sound waves to make pictures of the heart's size, structure and motion.

A healthcare professional might try to trigger AVNRT with other tests, which may include:

• Exercise stress test, which is typically done on a treadmill or stationary bicycle while the heart activity is watched.
• Electrophysiological study and cardiac mapping, which can show exactly where in the heart an irregular heartbeat starts.