AV Nodal Re-entry Arrhythmia
AV Nodal Re-entrant Tachycardia (AVNRT)
AVNRT is a type of supraventricular tachycardia. It is caused by a re-entrant electrical circuit that involves pathways within or near the AV node, and it can produce a sudden, fast and regular heartbeat.
On this page
Overview
What Is AVNRT?
The AV node is a small area of specialised tissue in the centre of the heart. Under normal conditions it acts as a gateway, passing the heart’s electrical signal from the upper chambers (the atria) to the lower chambers (the ventricles).
In AVNRT, an electrical impulse can travel in a repeating loop in and around the AV node. This is called re-entry. The loop can trigger a rapid, regular heartbeat that starts and stops suddenly.
AVNRT is one type of supraventricular tachycardia (SVT), meaning a fast rhythm that arises above the ventricles. It is a rhythm problem of the heart’s electrical system rather than a problem with the heart muscle or valves, and in many people the heart structure is otherwise normal.
Normal conduction
Normal AV Node Conduction
A normal heartbeat follows an ordered electrical route. The AV node adds a short, natural pause so that the chambers contract in sequence.
SA node
The heart’s natural pacemaker starts each beat.
Atria
The signal spreads across the upper chambers.
AV node
The signal pauses briefly at the gateway.
Ventricles
The signal spreads through the lower chambers.
A simplified outline of normal conduction.
Physiology
Dual-Pathway Physiology
In many people with AVNRT, the region around the AV node contains two electrical routes with different properties. They are often described as a fast pathway and a slow pathway.
Fast pathway
Conducts the signal quickly but needs longer to recover before it can conduct again.
Slow pathway
Conducts the signal more slowly but recovers sooner.
These terms describe a concept used by clinicians. Not every person’s AV node is identical, and the exact arrangement can differ from one person to another. Having two pathways does not by itself mean someone will have AVNRT.
Mechanism
How AVNRT Develops
The way AVNRT starts can be described in a few general steps. This is a high-level outline, not a description of every case.
A premature impulse
An early extra beat arrives at the AV node at a particular moment.
Different conduction
The two pathways respond differently: one may still be recovering while the other can conduct.
A re-entry circuit
The signal can travel down one route and return up the other, forming a loop.
Rapid repeated activation
Each trip around the loop can trigger another heartbeat, so the rhythm becomes fast and regular.
Comparison
AVNRT and Other SVTs
SVT is an umbrella term. Several rhythms share the same general description, but the mechanism and treatment approach can differ. Your care team uses the tests described below to work out which one applies.
AVNRT
A re-entry loop in or near the AV node, often involving two pathways.
AVRT (accessory pathway)
A loop that includes an extra electrical connection outside the AV node. See Wolff-Parkinson-White (WPW) syndrome.
Atrial tachycardia
A rapid rhythm that starts from a small area in the atria rather than from a loop.
For the broader picture, read the SVT page.
What you may notice
Symptoms
Some people have no symptoms between episodes. During an episode, people may notice:
- a sudden rapid heartbeat
- palpitations or a pounding feeling in the chest or neck
- dizziness or light-headedness
- shortness of breath
- chest discomfort
- weakness or tiredness
- near-fainting, in some people
Symptoms vary a great deal and do not always indicate a serious problem, but they should still be assessed. Episodes often start and stop suddenly and can last from a few minutes to longer.
If you have severe chest pain, fainting or severe breathlessness, seek urgent medical help.
Recording the rhythm
ECG
An ECG recorded during an episode may help identify a regular, narrow-complex tachycardia, which is the typical pattern for this group of rhythms. A resting ECG taken between episodes is often normal.
Because episodes may come and go, capturing a recording at the right time can be important. An ECG is one piece of information and is interpreted together with your history and other tests.
Finding the cause
Diagnosis
Diagnosis usually combines several steps, chosen by your care team to suit your situation:
- Symptom history
- ECG
- Holter monitoring
- Event recorder
- Electrophysiology study (EPS)
- SVT Ablation
Holter monitoring and event recorders can capture the rhythm over longer periods when symptoms come and go. An electrophysiology study may be considered where appropriate, for example when a clear answer is needed or when treatment is being planned.
Testing inside the heart
Electrophysiology Study
An electrophysiology study (EPS) uses thin catheters to record the heart’s electrical activity from inside the heart. Where clinically appropriate, it can help to identify:
- how the AV node conducts electrical signals
- the mechanism of the tachycardia
- whether dual-pathway physiology is present
- the area that may be treated
An EPS may be done on its own or as the first stage of a treatment procedure. Your care team will explain what is planned for you.
Locating the target
Slow-Pathway Mapping
When treatment is planned, the team needs to find the right area before any energy is delivered. In AVNRT the target is usually the region of the slow pathway, close to the AV node.
Clinicians may use catheter recordings and the electrical signals they see, sometimes together with imaging or mapping systems, to identify the region. The aim is to treat that small area while protecting the normal AV node conduction. Which tools are used depends on the procedure and the team.
First steps
Vagal Manoeuvres
Vagal manoeuvres are simple actions that stimulate the vagus nerve, which can slow conduction through the AV node. In some people with AVNRT, and in some other supraventricular tachycardias, they can end an episode. Examples include a controlled, forceful breath-out against resistance (the Valsalva manoeuvre) or, in some people, a cold stimulus to the face.
Their effect varies. They do not work for everyone, and a manoeuvre that has worked once may not work every time.
They are generally attempted while seated or lying down, ideally with someone nearby, and only by a person who is otherwise well. They should not be repeated persistently. Do not attempt them if you feel faint, or have chest pain or severe breathlessness. Seek urgent medical help in those situations.
Pressing on the neck is not advised. Your doctor can show you which manoeuvre, if any, is appropriate for you.
Ongoing care
When Episodes Keep Returning
Episodes that recur often, last a long time or need emergency care are a reason to see a cardiologist, even if they stop by themselves or with a manoeuvre. AVNRT often occurs in a structurally normal heart, but symptoms can be disruptive, and an ECG recorded during an episode helps to confirm the diagnosis.
Further assessment may include rhythm monitoring and, where suitable, an electrophysiology study. Options include observation, medicines chosen by your doctor (see Antiarrhythmic Medication) and catheter ablation (see SVT Ablation).
The choice depends on how often and how severely episodes occur, your preferences and your other health conditions.
Treatment
Catheter Ablation
Catheter ablation is a treatment that may be considered for AVNRT, depending on your symptoms, your preferences and your care team’s advice. For AVNRT it is commonly performed with radiofrequency (RF) ablation, although other energy sources can also be used.
Electrophysiology study
The rhythm and conduction are assessed.
Mechanism confirmed
The team confirms that AVNRT is the cause.
Slow-pathway target
The region to treat is identified.
Ablation
Energy is delivered to that small area.
Reassessment
The team checks the result.
Treatment options, benefits and risks differ between people. Your care team will discuss them with you.
The patient journey
Procedure Pathway
This is a general outline. Details vary, so follow the individual instructions provided to you.
Assessment
Your history and tests are reviewed.
Preparation
Your care team will advise you on preparation.
Procedure
Study and, where appropriate, ablation.
Recovery
You are monitored and given aftercare advice.
Follow-up
Your care team agrees next steps with you.
After treatment
Follow-Up
Follow-up depends on the treatment you had and how you feel afterwards. It may include a check-up, a review of any symptoms and, where clinically appropriate, an ECG or rhythm monitoring.
If you notice palpitations again, let your care team know. The timing and type of follow-up are decided individually.
Questions