AVNRT (AV Nodal Reentrant Tachycardia)

AVNRT Mechanism and ECG Example
AVNRT Mechanism and ECG Example
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What is AVNRT?

AVNRT (Atrioventricular Nodal Reentrant Tachycardia) is a arrhythmia that occurs in the AV node of the heart’s electrical conduction system and causes a sudden increase in heart rate. The heart rate typically ranges between 140-250 beats per minute, and the beats are usually regular. This condition occurs due to an abnormal electrical circuit in the AV node.

As the most common type of supraventricular tachycardia, AVNRT typically occurs in people without structural heart disease and is particularly more common in young to middle-aged women. Although it’s not life-threatening, it can significantly affect patients’ daily quality of life.

AVNRT episodes begin suddenly and can usually terminate spontaneously or with certain maneuvers. This arrhythmia can be successfully controlled with correct diagnosis and treatment.

How Does AVNRT Occur?

Electrical signals in our heart can travel through two different pathways when passing through the AV node. These are called the fast pathway and slow pathway. During a normal heartbeat, signals usually stimulate the heart by passing through the fast pathway. Signals traveling through the slow pathway become ineffective by conflicting with the fast ones. However, in some cases, an electrical circuit can form between these two pathways. This leads to AVNRT, a fast and regular arrhythmia.

This circuit can usually cause symptoms such as heart palpitations, dizziness, or weakness. In most cases, AVNRT doesn’t pose a serious risk but can be disturbing. Treatment usually involves medications or eliminating this circuit through a special procedure (ablation).

What Causes AVNRT?

AVNRT stems from an error in the electrical signals controlling heartbeats. This condition can be caused by heart diseases, congenital heart defects, sleep apnea, previous heart or lung surgeries, diabetes, thyroid gland problems, certain medications, and electrolyte imbalances. Additionally, factors such as excessive stress, fatigue, caffeine consumption, alcohol and smoking, sleep irregularity can trigger AVNRT episodes.

What are the Symptoms of AVNRT?

The most prominent symptom of AVNRT is sudden onset palpitations. Patients typically experience chest tightness or pressure, shortness of breath, and dizziness. Other common symptoms include noticeable pulse in the neck region, weakness, sweating, and anxiety. Some patients may experience chest pain, and rarely, fainting can occur.

How is AVNRT Diagnosed?

AVNRT is usually diagnosed through patient complaints (palpitations, dizziness, feeling faint) and ECG findings. A regular and rapid heart rhythm on ECG supports the diagnosis. If the arrhythmia hasn’t occurred, advanced tests such as Holter monitoring or electrophysiological study (EP Study) can be used to confirm the diagnosis.

AVNRT ECG Example
AVNRT ECG Example

How is AVNRT Treated?

AVNRT treatment is addressed in two stages: acute episode management and long-term treatment. During acute episodes, vagal maneuvers (Valsalva maneuver, cold application to face) can be tried first. When these methods are insufficient, medications such as adenosine, beta blockers, or calcium channel blockers are used. In very rare cases, cardioversion may be necessary.

For long-term treatment, beta blockers, calcium channel blockers, or antiarrhythmic drugs can be used. However, the most effective and permanent treatment method is ablation. The success rate of AVNRT ablation is over 95% and provides a permanent solution for many patients.

How is AVNRT Ablation Performed?

AVNRT ablation is performed through blood vessels from the groin area. Local anesthesia is administered before the procedure, and the patient is monitored. Special catheters are placed in the heart to record electrical signals around the AV node and surrounding areas. After determining the exact location, the target tissue is controllably heated or frozen using radiofrequency energy or cold energy. These energies are usually applied to the area called the slow pathway. Continuous monitoring is performed during the procedure to prevent AV block. After ablation is completed, the tachycardia is tested for recurrence, and normal conduction in the heart is confirmed. This procedure, which takes 1-2 hours, has a very high success rate.

In addition to these treatments, certain lifestyle changes are important to improve patients’ quality of life. Reducing caffeine consumption, regular sleep, stress management, quitting smoking, and limiting alcohol consumption are recommended.

What Happens If AVNRT Is Not Treated?

If AVNRT is not treated, it can lead to persistent symptoms such as palpitations, dizziness, and fatigue, which may significantly impact quality of life. In rare cases, prolonged or frequent episodes can result in tachycardia-induced cardiomyopathy, weakening the heart muscle. Additionally, the rapid heart rate might increase the risk of complications like blood clots or stroke. Therefore, timely treatment is important to prevent these potential risks.

What is the Course of AVNRT?

AVNRT is generally a benign rhythm disorder and is not life-threatening. However, it can pose a risk if there is an underlying heart condition such as heart failure, coronary artery disease, or serious valve problems. With correct diagnosis and appropriate treatment, the vast majority of patients return to their normal lives. The recurrence rate is very low, especially after ablation treatment. Regular check-ups and adherence to lifestyle changes play a key role in successful management of the condition.

Reference: AVNRT