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.