The main symptom of supraventricular tachycardia (SVT) is a very fast heartbeat that may last for a few minutes to a few days. The heart beats 100 or more times a minute. Usually during SVT, the heart beats 150 to 220 times a minute. The fast heartbeat may come and go suddenly.

Symptoms of supraventricular tachycardia may include:

• Pounding or fluttering feelings in the chest, called palpitations.
• A pounding sensation in the neck.
• Chest pain.
• Fainting or almost fainting.
• Lightheadedness or dizziness.
• Shortness of breath.
• Sweating.
• Weakness or extreme tiredness.

Some people with SVT do not notice symptoms.

In infants and very young children, symptoms of SVT may be vague. The symptoms can include sweating, poor feeding, a change in skin color and a rapid pulse. If your infant or young child has any of these symptoms, talk with a healthcare professional.

When to see a doctor

Supraventricular tachycardia (SVT) is usually not life-threatening unless you have heart damage or another heart condition. But if SVT is severe, the irregular heartbeat may cause all heart activity to suddenly stop. This is called sudden cardiac arrest.

Call a healthcare professional if you have a very fast heartbeat for the first time or if an irregular heartbeat lasts longer than a few seconds.

Symptoms of SVT may be related to a serious health condition. Call 911 or your local emergency number if you have a very fast heartbeat that lasts for more than a few minutes or if a fast heartbeat occurs with these symptoms:

• Chest pain.
• Dizziness.
• Shortness of breath.
• Weakness.

Supraventricular tachycardia (SVT) is caused by faulty signaling in the heart. Electrical signals in the heart control the heartbeat.

In SVT, a change in heart signaling causes the heartbeat to start too early in the heart's upper chambers. When this happens, the heartbeat speeds up. The heart can't fill with blood properly. Symptoms such as lightheadedness or dizziness can occur.

How does the heart beat?

To understand the cause of supraventricular tachycardia (SVT), it might help to know how the heart usually works.

The heart has four chambers:

• The two upper chambers are called the atria.
• The two lower chambers are called the ventricles.

Inside the upper right heart chamber is a group of cells called the sinus node. The sinus node makes the signals that start each heartbeat.

The signals move across the upper heart chambers. Then the signals arrive at a group of cells called the AV node, where they usually slow down. The signals then go to the lower heart chambers.

In a healthy heart, this heart signaling process usually goes smoothly. The heart usually beats about 60 to 100 times a minute at rest. But in SVT, the heart beats faster than 100 beats a minute. The heart may beat 150 to 220 times a minute.

Supraventricular tachycardia (SVT) is the most common type of arrhythmia in infants and children. It also tends to occur more often in women, particularly during pregnancy.

Health conditions or treatments that may increase the risk of supraventricular tachycardia include:

• Coronary artery disease, heart valve disease and other heart diseases.
• Heart failure.
• A heart problem present at birth, also called a congenital heart defect.
• Previous heart surgery.
• A sleep disorder called obstructive sleep apnea.
• Thyroid disease.
• Uncontrolled diabetes.
• Some medicines, including those used to treat asthma, allergies and colds.

Other things that may increase the risk of SVT include:

• Emotional stress.
• Too much caffeine.
• Excessive alcohol use, which is defined as 14 or more drinks a week for men and seven or more drinks a week for women.
• Smoking and nicotine use.
• Stimulant drugs, including cocaine and methamphetamine.

When the heart beats too fast, it may not send enough blood to the body. As a result, the organs and tissues may not get enough oxygen.

Over time, untreated and frequent attacks of supraventricular tachycardia (SVT) may weaken the heart and lead to heart failure. This is especially true in people who also have other medical conditions.

A severe attack of SVT may cause fainting or a sudden loss of all heart activity, called sudden cardiac arrest.

The same lifestyle changes used to manage supraventricular tachycardia (SVT) also may help prevent it. Try these tips.

• Follow a heart-healthy lifestyle. Eat a nutritious diet, don't smoke, get regular exercise and manage stress.
• Don't use a lot of caffeine. Avoid large amounts of caffeine. For most people with supraventricular tachycardia, moderate amounts of caffeine do not trigger episodes of SVT.
• Keep a notebook or diary of when symptoms happen. Include the symptoms, your heart rate and what you were doing at the time of the fast heartbeat. This information can help you learn the things that trigger the very fast heartbeat.
• Use medicines carefully. Some medicines, including those bought without a prescription, may contain stimulants that can trigger SVT.

To diagnose supraventricular tachycardia (SVT), a healthcare professional examines you and listens to your heart. A member of your care team takes your blood pressure. You are usually asked questions about your symptoms, health habits and medical history.

Tests

Tests to diagnose supraventricular tachycardia (SVT) may include:

• Blood tests. A sample of blood is taken to check for other causes of a fast heartbeat, such as thyroid disease.
• Electrocardiogram (ECG or EKG). This quick test checks the heartbeat. Sticky patches, called electrodes, attach to the chest and sometimes to the arms or legs. An ECG shows how fast or how slow the heart is beating. Some personal devices, such as smartwatches, can do ECGs. Ask your care team if this is an option for you.
• Holter monitor. This portable ECG device is worn for 1 to 2 days to record the heart's activity during daily activities. It can spot irregular heartbeats that aren't found during a regular ECG.
• Event recorder. This device is like a Holter monitor, but it records only at certain times for a few minutes at a time. It's typically worn for about 30 days. You usually push a button when you feel symptoms. Some devices automatically record when an irregular heartbeat occurs.
• Implantable loop recorder. This device records the heartbeat continuously for up to three years. It's also called a cardiac event recorder. It shows how the heart is beating during daily activities.
• Echocardiogram. Sound waves are used to create images of the beating heart. This test can show how blood flows through the heart and heart valves.

Other tests that may be done to diagnose SVT include:

• Exercise stress test. Exercise may trigger or worsen supraventricular tachycardia. During a stress test, you usually exercise on a treadmill or stationary bicycle while the heart activity is checked. If you can't exercise, you may be given medicine that increases the heart rate like exercise does. Sometimes an echocardiogram is done during a stress test.
• Tilt table test. This test may be done to learn if a fast heartbeat leads to fainting. Your heart rate, heart rhythm and blood pressure are checked while you lie flat on a table. Then, under careful supervision, the table is tilted to a standing position. A member of your care team watches how your heart and nervous system respond to the changes in position.

• Electrophysiological (EP) study. This test helps show where faulty heart signals start in the heart. An EP study is mostly used to diagnose some specific types of tachycardias and irregular heartbeats.

  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.

Most people with supraventricular tachycardia (SVT) don't need treatment. If the very fast heartbeat happens often or lasts for a long time, your care team may suggest treatment.

Treatment for SVT may include:

• Carotid sinus massage. The carotid arteries are the two main blood vessels that send blood to the head and brain. There is one on each side of the neck. During carotid sinus massage, a healthcare professional gently presses on a specific area of the neck by the carotid artery. This makes the body release chemicals that slow the heart rate. Carotid massage should only be done by an experienced healthcare professional. Do not do carotid sinus massage on your own.
• Vagal maneuvers. Simple but specific actions such as coughing, bearing down as if passing stool or putting an ice pack on the face can help slow down the heart rate. These actions affect the vagus nerve, which helps control the heartbeat.
• Medicines. If SVT happens frequently, medicines may be given to control the heart rate or reset the heart rhythm. It's very important to take the medicine exactly as directed in order to reduce complications.
• Cardioversion. Paddles or patches on the chest deliver shocks that reset the heart rhythm. This treatment is generally used when emergency care is needed or when vagal maneuvers and medicines don't work. It's also possible to do cardioversion with medicines.
• Catheter ablation. In this treatment, a doctor inserts one or more thin, flexible tubes called catheters through a blood vessel, usually in the groin. Sensors on the tip of the catheter use heat or cold energy to create tiny scars in the heart. The scars block faulty heart signals that cause the irregular heartbeat.
• Pacemaker. Rarely, a small device called a pacemaker is needed to help the heart to beat. It stimulates the heart as needed to keep it beating regularly. A pacemaker is placed under the skin near the collarbone in a minor surgery. Wires connect the device to the heart.

If you have supraventricular tachycardia, a heart-healthy lifestyle is an important part of your treatment plan.

Try these tips to keep the heart healthy:

• Don't smoke. Smoking is a major risk factor for heart disease. If you smoke and can't quit, talk to your care team about programs or treatments that can help.
• Eat healthy foods. Choose fruits, vegetables and whole grains. Limit salt and saturated fats.
• Get regular exercise. Exercise at least 30 minutes a day on most days of the week. Talk to your healthcare team about the amount and type of exercise that's best for you.
• Maintain a healthy weight. Being overweight increases the risk of heart disease. Ask your healthcare team what weight is best for you.
• Control high blood pressure, high cholesterol and diabetes. Make lifestyle changes and take medicines as directed. Get regular health checkups.
• Manage stress. Find ways to help reduce emotional stress. Practicing mindfulness and joining a support group are some ways to reduce and control stress. If you have anxiety or depression, talk to your care team about strategies to help.
• Get good sleep. Poor sleep may increase the risk of heart disease and other health conditions. Adults should aim for 7 to 9 hours daily.
• Limit alcohol. If you choose to drink alcohol, do so in moderation. For healthy adults, that means up to one drink a day for women and up to two drinks a day for men.

Stress-relief techniques, such as meditation and yoga, might help slow the heartbeat.

If you have an unusually fast heartbeat, make an appointment for a health checkup. If a very fast heartbeat lasts longer than a few minutes, get medical care right away.

You may be referred to 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 brief. Because there's often a lot to discuss, it's a good idea to be prepared for your appointment. Here's some information to help you get started.

What you can do

When you make the appointment, ask if there's anything you need to do in advance, such as avoid foods or drinks. You may need to do this if your care team orders any tests.

Make a list ahead of time that you can 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 recent life changes.
• All medicines that you take. Include vitamins, supplements and medicines bought with and without a prescription. Also include the dosages.
• Questions to ask your care team.

For supraventricular tachycardia, basic questions to ask your healthcare professional include:

• What is the likely cause of my fast heart rate?
• What kinds of tests do I need?
• What's the most appropriate treatment?
• What are the risks of SVT?
• How often do I need health checkups?
• How do other conditions I have or medicines I take affect my heartbeat?
• Do I need to avoid or stop doing any activities?
• Is there any printed information that I can take home with me? What websites do you recommend?

Don't hesitate to ask additional questions.

What to expect from your doctor

Your healthcare team is likely to ask you many questions. Being ready to answer them may save time to go over any details you want to spend more time on. Your care team may ask:

• When did the symptoms start?
• How often do you have a fast heartbeat?
• How long does the fast heartbeat last?
• Does anything, such as exercise, stress or caffeine, make the symptoms worse?
• Does anyone in your family have heart disease or a history of irregular heartbeats?
• Has anyone in your family had sudden cardiac arrest or died suddenly?
• Do you smoke or have you ever smoked?
• How much alcohol or caffeine do you use, if any?
• What medicines do you take?
• Do you have high blood pressure, high cholesterol, diabetes or other conditions that may affect your heart health?