What is atrioventricular nodal reentrant tachycardia (avnrt)?

Atrioventricular nodal reentrant tachycardia (AVNRT) is a heart condition characterized by a heart rate faster than normal, usually above 100 beats per minute. Episodes typically begin and end suddenly, forcing the heart to work overtime to pump blood more quickly.

AVNRT occurs when the heart’s electrical impulses move in a circular pattern and re-enter areas they have already passed through. It is the most common type of supraventricular tachycardia and most frequently affects young women.

The condition originates in the atrioventricular (AV) node, which is the connection point of the heart’s conduction system between the atria and the ventricles. Its function is to momentarily slow down the cardiac impulse for a few milliseconds, giving the atria time to contract before the ventricles do.

Although its exact origin is unknown, AVNRT is caused by the presence of additional pathways in the AV node. These pathways are present from birth but cause an arrhythmia after the heart has fully developed, usually when the person is between 20 and 30 years old.

AVNRT is one of the most common forms of paroxysmal supraventricular tachycardia.

Symptoms typically begin suddenly, and the patient may experience rapid and regular palpitations ranging from 150 to 250 beats per minute. The palpitations can be accompanied by a feeling of chest tightness, shortness of breath, dizziness, or a sensation of general weakness.

These episodes frequently occur in young, healthy individuals but can also happen in older adults.

Beyond palpitations, some people may experience anxiety, sweating, and, in severe cases, syncope (a brief loss of consciousness) due to a temporary decrease in cardiac output.

These symptoms usually disappear quickly, just as they began, especially if the episode ends spontaneously or with vagal maneuvers like the Valsalva maneuver.

While AVNRT is not usually a dangerous condition on its own, it can impact a patient’s quality of life and requires medical evaluation to confirm the diagnosis.

How is AVNRT Diagnosed?

The diagnosis of AVNRT is mainly based on an electrocardiogram (ECG), especially if a recording is taken during an episode.

A typical AVNRT ECG shows a regular tachycardia with narrow QRS complexes, which means the heart’s ventricles are contracting quickly and efficiently, along with a high heart rate.

The baseline ECG may be completely normal, so ambulatory monitoring with a 24-hour Holter monitor or event recorders may also be used if episodes are infrequent.

To confirm the diagnosis, an intracardiac electrophysiology study may be used in some cases. This procedure allows the doctor to induce the tachycardia in a controlled environment and map the reentrant circuit in the AV node. This evaluation not only confirms the diagnosis of AVNRT but also helps in planning a definitive treatment.

The treatment for AVNRT varies depending on its frequency and severity. In acute cases, when the tachycardia is ongoing, it can be stopped using vagal maneuvers, such as the Valsalva maneuver or facial immersion in cold water, which help stimulate the vagus nerve and can interrupt the reentrant circuit.

If these maneuvers are not effective, a drug that temporarily blocks conduction through the AV node can be administered intravenously. This safely and quickly stops the tachycardia.

For patients with recurrent episodes or significant symptoms, the most effective definitive treatment is radiofrequency catheter ablation. This minimally invasive procedure destroys the focus of the reentrant circuit in the AV node, leading to a cure in almost all cases. Ablation is a procedure especially used in young people.

At the Arrhythmia Clinic at ABC Medical Center, we can provide you with specialized care. Contact us!