As the most common type of supraventricular tachycardia, atrioventricular nodal reentry tachycardia (AVNRT) has episodes that often start and end suddenly. To get oneself diagnosed, the doctor may suggest undergoing tests and procedures such as blood tests, electrocardiogram, holter monitor or echocardiogram. They are applied for different purposes. For example, your thyroid function is checked during blood tests. By applying the electrocardiogram, the electrical activity of your heart is measured. To further identify the trigger of the episode, you may be asked to do test such as stress test, or electrophysiological testing and mapping.