Atrioventricular Nodal Reentrant Tachycardia (AVNRT) is an arrhythmia caused by an abnormal short circuit in the region of your heart called the AV node. This short circuit causes electrical signals to enter a loop like a coil. It is the most common type of supraventricular tachycardia. Your heart suddenly starts beating very fast and regularly, between 140 and 250 beats per minute.
What is AVNRT?
AVNRT is a type of tachycardia that occurs due to recurring (reentrant) electrical cycles that occur within or very close to the atrioventricular (AV) node of the heart. This condition, usually seen in young and healthy individuals, does not create a life-threatening situation for most people but can significantly reduce quality of life.
What are the symptoms of AVNRT?
During AVNRT, your heart suddenly speeds up and this acceleration is often noticeable. Attacks can last from a few seconds to several hours. Palpitation sensation is the most common symptom, but dizziness, chest discomfort, shortness of breath, weakness, and sometimes fainting can also be seen.
Symptoms start suddenly and end suddenly. Physical exertion, stress, caffeinated drinks, or alcohol can trigger attacks. While symptoms remain mild in some people, they can cause discomfort severe enough to disrupt daily life in others.
What causes AVNRT?
The basic cause of AVNRT is the dual electrical pathway structure found congenitally in the AV node. This dual pathway causes electrical stimuli to return under certain conditions and create a continuous cycle. Genetic predisposition, some heart diseases, or structural disorders can increase the risk. Often the first attack starts at a young age, but it can be seen at any age.
The main conditions leading to AVNRT are:
- AVNRT does not result from a defect in your heart’s structure, but from the congenital formation of pathways in the AV node in a different way. This is a result of genetic predisposition.
- Although the abnormal pathway exists from birth, there are some triggering factors that initiate attacks. These include excessive fatigue, stress, caffeine, alcohol, cold medicine, and hormonal changes (especially menstrual period in women).
- Intense exercise can also trigger an AVNRT attack by causing your heart to speed up.
Who develops AVNRT?
AVNRT usually occurs in structurally healthy hearts. It is seen twice as often in women compared to men. It is most commonly diagnosed in young adults aged 20-40. However, it can also be encountered at advanced ages. Family history, thyroid disorders, working under intense stress, excessive stimulant use (energy drinks, excessive coffee) are factors that increase risk.
How is AVNRT diagnosed?
AVNRT diagnosis is often made with ECG. However, since attacks are short-lived, sometimes the rhythm may have returned to normal when ECG is taken. In this case, Holter device (24-48 hour rhythm recording) or event recorders are used. Electrophysiological study (EP Study) is the gold standard in definitive diagnosis and treatment planning.
The main methods used in AVNRT diagnosis are:
- An ECG taken during an attack shows your heart’s fast and regular rhythm, along with some electrical features specific to AVNRT.
- Holter monitor is a portable device that continuously records your heart’s rhythm for 24 hours or longer. This way, rarely seen attacks can be detected.
- Electrophysiological study (EPStudy) test can be used to confirm AVNRT diagnosis. Catheters are placed in your heart to examine the electrical system, the cyclical pathway causing AVNRT is found, and during the test, an attack is triggered and monitored on ECG.
How is AVNRT treated?
The purpose of AVNRT treatment is to stop palpitation attacks, reduce the frequency of attacks, and improve the patient’s quality of life. Treatment usually includes vagal maneuvers applied during attacks, drug therapy, or catheter ablation method that offers a permanent solution.
The methods applied in AVNRT treatment are:
Vagal maneuvers
When an attack starts, some physical maneuvers can slow your heart’s rhythm and stop the attack. These maneuvers include coughing, drinking cold water, or Valsalva maneuver (straining movement).
Drug therapy
In people who have frequent attacks, medications such as beta blockers or calcium channel blockers can be used to prevent AVNRT. In emergency situations, medications can be given intravenously to stop attacks.
Catheter ablation
This is the most effective and permanent treatment method for AVNRT. The abnormal conduction pathway found during electrophysiological study is burned or destroyed with radiofrequency energy or freezing (cryoablation) method. This procedure permanently terminates the AVNRT cycle. The success rate of ablation is over 95%.
What are the risks of AVNRT?
AVNRT is usually a benign arrhythmia, but risks such as fainting, falling, or rarely heart failure can occur during attacks if the frequency and duration of attacks are high. Long-lasting and very fast attacks can temporarily reduce the heart’s pumping power.
How is AVNRT prevented?
Since AVNRT is a congenital condition, it is not possible to prevent its occurrence. However, you can make some lifestyle changes to reduce the frequency and severity of attacks. These measures help prevent triggering of attacks by improving your quality of life.
What you can do to prevent AVNRT attacks:
- If factors such as caffeine, alcohol, excessive fatigue, and stress trigger AVNRT attacks, avoid these factors.
- Regular and light exercise, healthy eating, and adequate sleep support your heart’s general health.
- Regularly use the medications your doctor has given to prevent AVNRT.
When should you consult a doctor?
Although AVNRT attacks are usually not dangerous, you need to consult a doctor for constantly recurring attacks or attacks that seriously affect your quality of life. Emergency medical evaluation is required in the following situations:
- If you faint or feel like you’re going to faint during a palpitation attack
- If you experience severe chest pain, shortness of breath, or sweating accompanying palpitations
- If you experience a long-lasting palpitation attack that does not subside with vagal maneuvers or rest
- If you have newly started palpitations that bother you
Reference: AVNRT
