Atrioventricular Nodal Reentrant Tachycardia (AVNRT)

Atrioventricular nodal reentrant tachycardia (AVNRT) is a type of abnormal heartbeat (arrhythmia). You have episodes where your heart suddenly starts beating very fast — typically over 120 beats per minute. AVNRT is one of the most common types of supraventricular tachycardia (SVT), or fast heartbeats that begin in your heart’s upper chambers.

Here’s what each part of AVNRT means:

• Atrioventricular: “Atrio” refers to atrium (top heart chamber), and “ventricular” refers to ventricle (bottom heart chamber). You might see atrioventricular called “AV” for short.
• Nodal: This refers to a “node,” or a small area of tissue in your heart that controls electrical signals. “Atrioventricular nodal” refers to the AV node near the center of your heart.
• Reentrant: Normally, electrical signals follow a set path through your heart. But with AVNRT, they tend to reenter a circular path in your AV node. This causes a fast heartbeat.
• Tachycardia: This is the medical term for a fast heart rate. There are many different types of tachycardia. AVNRT is just one example.

AVNRT can affect people at any age, but it often starts around age 30. It’s more common in females than in males. AVNRT can occur in young, otherwise healthy adults.

Symptoms of AVNRT

This condition can make you uncomfortably aware of your heartbeat. Symptoms can include:

• Heart palpitations — this is the most common symptom
• Feeling like your heart is racing
• Dizziness
• Palpitations or discomfort in your neck
• Producing more pee than usual (polyuria)
• Shortness of breath

If you’re wearing a heart rate monitor, you might see your heart rate jump to between 120 and 200 beats per minute (bpm). This is higher than the normal adult heart rate, which is 60 to 100 bpm at rest. It’s also possible for AVNRT to make your heart rate go above 200 bpm, but this is more likely in younger people.

Symptoms occur in episodes that come and go. An episode might last just a few seconds or as long as several hours. Episodes start and stop suddenly.

AVNRT causes

Like other arrhythmias, this occurs when there’s abnormal electrical activity in your heart. In this case, the problem relates to your AV node.

Your AV node has a reputation for being the “gatekeeper” between your upper heart chambers (atria) and lower heart chambers (ventricles). It makes sure electrical signals get from your atria to your ventricles along a precise path.

With atrioventricular nodal reentrant tachycardia, electrical signals get caught up in your AV node. Instead of going toward your ventricles, they go around in circles in the node. When this happens, your heart can start beating very fast.

To picture this, think of cars going around and around in a traffic circle instead of exiting to a street. Normally, signals should “exit” the node and travel toward your ventricles.

What triggers an AVNRT episode?

It’s not always clear what triggers an episode of AVNRT. It sometimes happens on its own for no known reason. But possible triggers include alcohol, caffeine and physical activity.

How doctors diagnose this condition

Healthcare providers diagnose AVNRT by doing a physical exam and talking to you about your symptoms. They may also do one or more of the following tests:

• Electrocardiogram (ECG/EKG) to check your heart’s electrical activity
• Holter monitor to try and document the arrhythmia if it doesn’t occur during your EKG
• Electrophysiologic study to get detailed insights about your heart’s electrical activity
• Echocardiogram (echo) to check your heart structure and function
• Blood tests to look for conditions that might be affecting your heart

Types of AVNRT

Healthcare providers classify AVNRT into the following types:

• Typical AVNRT: This is also called slow/fast AVNRT. It’s the most common type, affecting about 85 to 90 out of every 100 people with the condition. It means an electrical signal follows a slow pathway and then a fast one in your AV node.
• Atypical AVNRT: This type is much less common. There are two subtypes — fast/slow and slow/slow. These terms describe the pathways electrical signals take in your AV node.

You can’t tell which type you have based on your symptoms. But your provider can see these differences with a diagnostic electrophysiology study (EPS).

How is AVNRT treated?

AVNRT treatment aims to manage your symptoms and improve how you feel from day to day. Unlike some other arrhythmias, AVNRT isn’t life-threatening. But episodes of a very fast heart rate can feel scary or disrupt your life.

Your healthcare provider will talk to you about your treatment options and help you decide what’s best for your unique needs. Certain treatments can stop an episode in its tracks. Others prevent episodes by helping your heart’s electrical system work as it should.

Treatments that can stop an episode include:

• Vagal maneuvers: These are physical actions you take that can lower your heart rate. A provider helps you perform these maneuvers in a safe, clinical setting. You should only do these at home if your provider recommends it and teaches you how.
• Medicines: Your provider may give you a medicine called adenosine through an IV. It’s highly effective at getting your heart rate back to normal. Other options include certain beta-blockers and calcium channel blockers.
• Cardioversion: Your provider uses a device or medicine to safely lower your heart rate. This procedure is typically done if other treatments don’t work or aren’t an option for you.

If you have frequent or severe AVNRT episodes, your provider may recommend treatments to prevent these from occurring. Such treatments help keep your heart’s electrical signals from taking the abnormal, circular route through your AV node. Options include:

• Catheter ablation: This procedure blocks abnormal electrical signals in your AV node to help your heart beat normally. It can often cure AVNRT, so you won’t have any more episodes.
• Long-term use of medicine: Taking certain medicines long-term is another option for preventing episodes. Providers typically prescribe verapamil, diltiazem or beta-blockers. If those don’t work for you, your provider may prescribe flecainide or propafenone.

When should I see my healthcare provider?

If you’re diagnosed with AVNRT, it’s important to follow the appointment schedule your provider gives you. These give your provider a chance to check in with you about how you’re feeling.

Call your provider right away if:

• Your symptoms change or get worse
• You have questions about your treatment plan
• You experience any side effects from your medicines

What can I expect if I have this condition?

AVNRT can cause uncomfortable symptoms, but it doesn’t pose a serious threat to your health. Your provider will help you understand your options for stopping episodes and, if needed, preventing future ones.

If you rarely have episodes and your symptoms are mild, your provider may recommend waiting to try treatments like cardioversion or long-term use of medicine. It’s possible you might eventually stop having any episodes even without these treatments. Your provider will help you understand what to expect in your situation.

What’s the difference between AVNRT and AVRT?

It can be easy to confuse two arrhythmias that have similar-sounding names. But AVNRT isn’t the same as AVRT. The “N,” which stands for “nodal,” is important in AVNRT. It refers to the location of the abnormal electrical activity — your AV node.

AVRT is different because the problem is that there’s an extra (accessory) pathway that sends electrical signals from your atria to your ventricles. In other words, your heart has an additional wire that’s not supposed to be there and causes a fast and abnormal heart rhythm. AVRT is a feature of Wolff-Parkinson-White syndrome.