Atrioventricular nodal reentry tachycardia (AVNRT) is a type of irregular heartbeat, also called an arrhythmia. It is the most common type of supraventricular tachycardia (SVT).

People with AVNRT have a very fast heartbeat that often starts and ends suddenly. In AVNRT, the heart beats more than 100 times a minute. The condition is due to a change in heart signaling.

AVNRT tends to occur more often in young women. But anyone can have it at any age. AVNRT may not need treatment. When treatment is needed, it may include specific actions or movements, medicines, or a heart procedure.

Atrioventricular nodal reentry tachycardia (AVNRT) is caused by faulty electrical signaling in the heart. Electrical signals control the heartbeat.

Usually, electrical signals in the heart follow a specific pathway. In AVNRT, there is an extra signaling pathway, called a reentrant circuit. The extra pathway makes the heart beat too early. This stops the heart from pumping blood like it should.

Healthcare professionals aren't sure why some people have the extra pathway that causes AVNRT. Sometimes, changes in the heart's structure may cause it.

Possible complications of AVNRT are:

• Worsening of existing heart disease.
• Sudden stopping of all heart activity, called sudden cardiac arrest.

If you have a very fast heartbeat that often starts and ends suddenly, make an appointment for a health checkup. If a fast heartbeat lasts more than a few minutes, get medical care right away.

You may see a doctor trained in heart conditions, called a cardiologist. You also might see a doctor trained in heart rhythm disorders, called an electrophysiologist.

Appointments can be short, so it's good to be prepared. Here's some information to help you get ready for your visit.

What you can do

When you make the appointment, find out if there's anything you need to do in advance. For example, you may be told not to eat or drink before some tests.

Make a list to share with your healthcare team. Your list should include:

• Any symptoms, including those that may seem unrelated to your heart.
• Important personal information, including any major stresses or big life changes.
• All medicines you take. Write down any vitamins, supplements and medicines bought with and without a prescription. Include the doses.
• Questions to ask your care team.

For atrioventricular nodal reentry tachycardia (AVNRT), some questions to ask your healthcare professional include:

• What is causing my rapid heart rate?
• What tests do I need?
• What treatment is right for me?
• What are the risks of AVNRT?
• How often do I need checkups?
• How do other conditions I have or medicines I take affect my heartbeat?
• Do I need to change my activities or what I eat and drink?
• Do you have information I can take home with me? What websites do you suggest?

Don't hesitate to ask any other questions.

What to expect from your doctor

Your healthcare team is likely to ask you many questions. Being ready to answer them can save time to talk about any other concerns. Your care team may ask:

• When did your symptoms start?
• How often do you have a fast heartbeat?
• How long does it last?
• Does anything make your symptoms worse?
• Does anyone in your family have a fast heartbeat or other heart condition?
• Has anyone in your family ever died suddenly or had sudden cardiac arrest?
• Have you ever smoked, or do you smoke now?
• Do you use alcohol or caffeine? If so, how much and how often?
• What medicines are you taking?
• Do you have health issues such as high blood pressure, high cholesterol, diabetes or another condition that could affect your heart?

Atrioventricular nodal reentry tachycardia (AVNRT) is more common in young women. But anyone can get it.

Some health conditions or treatments may increase the risk of AVNRT. These include:

• Coronary artery disease, heart valve disease and other heart diseases.
• Heart failure.
• Heart condition present at birth, called a congenital heart defect.
• Previous heart, lung or throat surgery.
• Obstructive sleep apnea.
• Thyroid disease.
• Lung diseases such as chronic obstructive pulmonary disease (COPD).
• Diabetes that is not controlled.
• Some medicines, including those used to treat asthma, allergies and colds.

Other things that may increase the risk of AVNRT include:

• Emotional stress.
• Caffeine.
• Excessive alcohol use, which is defined as 15 or more drinks a week for men and eight or more drinks a week for women.
• Smoking and using nicotine.
• Stimulant drugs, including cocaine and methamphetamine.

To diagnose atrioventricular nodal reentry tachycardia (AVNRT), a healthcare professional examines you and asks questions about your symptoms and medical history. The healthcare professional listens to your heart and lungs using a stethoscope.

Tests are often done to check heart health.

Tests

Tests used to diagnose atrioventricular nodal reentry tachycardia (AVNRT) may include:

• Blood tests. Blood tests can check for thyroid disease and other conditions that can cause an irregular heartbeat.
• Electrocardiogram (ECG or EKG). This simple test checks the electrical activity of the heart. It shows how fast or slow the heart is beating.
• Holter monitor. This portable ECG device is worn for a day or more to record the heart's activity during daily activities. A Holter monitor can find irregular or fast heartbeats that don’t show up on a regular electrocardiogram.
• Echocardiogram. Sound waves create pictures of the beating heart. An echocardiogram shows the heart's size and how blood flows through the heart.
• Exercise stress tests. These tests often involve walking on a treadmill or riding a stationary bike while the heart activity is watched. Exercise tests show how the heart reacts to physical activity. If you can't exercise, you might get medicines that affect the heart like exercise does.
• Electrophysiological study. Also called an EP study, this test can show where in the heart the irregular heartbeat starts. During this test, a doctor guides one or more flexible tubes through a blood vessel, usually in the groin, to various areas in the heart. Sensors on the tips of the tubes record the heart's electrical signals.

A very fast heartbeat is the most common symptom of atrioventricular nodal reentry tachycardia (AVNRT). In AVNRT, the heart can beat between 120 to 280 times a minute. The fast heartbeat usually starts suddenly.

AVNRT does not always cause symptoms. When symptoms do show up, they may include:

• A pounding feeling in the neck.
• Pounding or fluttering heartbeat, called palpitations.
• Chest pressure, tightness or pain.
• Dizziness or lightheadedness.
• Shortness of breath.
• Sweating.
• Weakness or extreme tiredness.
• Fainting or almost fainting.

Symptoms of AVNRT may be mild in children. Some symptoms include sweating, trouble feeding, changes in skin color and a fast heartbeat.

When to see a doctor

Make an appointment for a healthcare checkup if you have unexplained changes in your heartbeat.

Also see a healthcare professional if an infant or child has these symptoms:

• Fast heartbeat.
• Sweating for no reason.
• Changes in feeding.
• Changes in skin color.

Call 911 or your local emergency number if you a very fast heartbeat that lasts for several minutes or happens with these symptoms:

• Chest pain.
• Dizziness.
• Trouble breathing.
• Weakness.