Supraventricular Tachycardia (SVT): What Is It?

Medically Reviewed by Zilpah Sheikh, MD on November 10, 2023
11 min read

 

Supraventricular tachycardia (SVT) is a type of arrhythmia, or an irregular heartbeat, where your heart beats erratically or fast. Also called paroxysmal supraventricular tachycardia, SVT affects the upper chambers of your heart.

The name is from Latin. Supraventricular means "above the ventricles," which are the lower two sections of your heart. Tachycardia, pronounced (tack-eh-CARD-ee-uh), is what doctors call a fast heartbeat.

Bouts of SVT can last from a few seconds to a few hours, and your heart can beat as fast as 220 times a minute.

During an episode, you might have a drop in blood pressure and feel dizzy or lightheaded. Other times, the only thing you feel is your rapid heartbeat. SVT usually doesn't cause serious health problems, but you should see your doctor if you have symptoms.

SVT vs. VTACH

People sometimes confuse SVT with a similar condition called ventricular tachycardia (VTACH). VTACH is also a type of an irregular heartbeat. But it starts in your heart's ventricles, which are the lower two chambers, instead of your heart's atria, the upper two chambers.

VTACH is more common in older people with underlying heart issues. Usually, SVT isn't as serious as VTACH.

Who does SVT affect?

SVT usually affects younger people. It often starts when you're in your teens or early 20s. But young children, middle-aged people, or older people can also have SVT. SVT is more common in women or those assigned female at birth, especially during pregnancy.

Your heart is a muscular organ that pumps about 2,000 gallons of blood a day to send oxygen-rich blood to your body. It has four pumping chambers to do the job: the left and right atria at the top and the left and right ventricles on the bottom.

Your heart also has something of a natural pacemaker. It's called the sinoatrial node or SA node. It's at the top of your heart and sends electrical signals that keep it beating the right way.

The electrical signal from the SA node makes the muscles of the upper two chambers squeeze, pumping blood into the lower two chambers. Then the signal moves down and causes the muscles of the lower two chambers to squeeze. That sends blood to your body.

The heart beats like this in a familiar "lub-dub" pattern some 50-99 times a minute if you're at rest.

The heartbeat normally raises and drops in speed based on signals that get sent to the SA node. During a bout of SVT, these signals don't happen normally. The electrical signals in the upper chambers fire off early, causing them to squeeze too soon. That interrupts the main electrical signal coming from the SA node. This makes the heart beat very quickly and irregularly.

There are a few types of SVT:

Atrioventricular (AV) nodal reentrant tachycardia: This is the most common form, especially among young women. If you have it, there's an extra pathway in your heart near the AV node. This pathway, known as a reentrant circuit, causes an electrical signal to circle around and around instead of moving down to your heart's lower chambers. This triggers the sudden, rapid heartbeat.

AV reciprocating tachycardia: This happens when you have an abnormal pathway linking your heart's upper and lower chambers causing the signal to move around and around in a big loop. This type of SVT is more common in younger people. It also affects people with an inherited condition called Wolff-Parkinson-White syndrome.

Atrial tachycardia: This happens when a short circuit in your heart's right or left atrium triggers a faulty electrical signal. It usually affects people who have heart disease.

Sinus tachycardia: This is when your heart beats quickly but at a normal rhythm. A fast heartbeat is normal with exercise or stress but shouldn't happen when you're resting. Causes of this type of SVT include certain medications, illegal drugs, fever, pain, and some medical conditions. If a faster heartbeat doesn't go away when the stressful situation ends or you stop exercising, talk with your doctor. Sinus tachycardia usually isn't dangerous, but your doctor can rule out more serious heart-related issues.

Paroxysmal SVT: "Paroxysmal" means that something happens in occasional bursts. This type of SVT usually affects young people who do engage in intense exercise.

Other tachycardia

There are several other types of tachycardia, including:

  • Sinus nodal reentrant tachycardia
  • Junctional ectopic tachycardia
  • Nonparoxysmal junctional tachycardia
  • Premature atrial contractions
  • Accessory pathway tachycardias such as Wolff-Parkinson-White syndrome
  • Multifocal atrial tachycardia
  • Atrial fibrillation
  • Atrial flutter

SVT is usually caused by things you can't control, such as a medical condition or previous surgery. Sometimes, an episode is triggered by stress, exercise, or lack of sleep, though it usually happens without any obvious reason.

Medical conditions

Health conditions that can cause your heart to race include:

  • Lung disease
  • Thyroid disease
  • Heart failure or other heart disease
  • Wolff-Parkinson-White syndrome

Certain medications

Some medications for asthma, allergies, and colds can affect your heartbeat. Talk with your doctor if you're concerned that your medications might be causing SVT episodes.

Congenital issues

"Congenital" means something that you're born with. Some people are born with an extra electrical pathway or abnormal electrical circuits in their heart that can cause arrhythmias like SVT.

Heart surgery

If you've had heart surgery, scar tissue can change how electrical signals pass through your heart.

Other things that can trigger SVT

Your heart is more likely to race when you:

  • Are under a lot of stress
  • Have anxiety
  • Drink a lot of caffeine and alcohol
  • Smoke or use tobacco
  • Abuse drugs like cocaine or methamphetamine, also called crystal meth
  • Are pregnant

You're at a high risk of some types of SVT if you're middle-aged or older and when you're pregnant.

Several health conditions raise your risk, including:

  • Heart disease (coronary artery disease, heart failure, disease of the heart muscle or valve)
  • Lung disease
  • Thyroid disease
  • Diabetes
  • Sleep apnea

Smoking and using illicit drugs are also risk factors for SVT.

During SVT, you might have a rapid heartbeat or heart palpitations (feeling like your heart is pounding or fluttering). When your heart beats too fast, it doesn't have time to fully refill with blood between beats. That means it can't send enough blood to your body. This can cause:

  • Chest pain
  • Dizziness
  • Fatigue
  • Shortness of breath
  • Fainting
  • Sweating
  • Weakness
  • A pounding feeling in the neck

Rarely, SVT can cause unconsciousness or cardiac arrest. And sometimes, SVT doesn't cause any symptoms.

It might be harder to notice symptoms in young children. In infants, look for sweating, pale skin, fast pulse, vomiting, and poor feeding.

If you feel like your heart is fluttering and you have any of these symptoms, call your doctor to be tested for SVT.

If you have symptoms, your doctor will ask you detailed questions.

They'll want to know how old you were when you first noticed a problem. They'll also ask when and how your symptoms began. That includes whether you were exercising when you noticed things such as a rapid pulse, dizziness, or a hard time breathing.

Other things they'll ask you about:

  • Whether your symptoms came on suddenly or slowly
  • What they feel like and how long they last
  • If you have a fast heartbeat after caffeine or stress
  • If you or anyone in your family has had heart problems or procedures

During your exam, your doctor will listen to your heart and lungs with a stethoscope. They might also:

Electrocardiogram (EKG) test

If your doctor suspects you have SVT, they want you to have an EKG.

This test records your heart's rhythm over time, so if it's not beating as it should, it can tell your doctor what the problem is.

To set up the test, a nurse or technician will attach six sticky patches that stick to you skin called electrodes on your chest and others on your arms and legs. If you have a hairy chest, an aide may need to shave small areas so they stay on.

Each patch is attached to a wire that leads to a machine. During the short test, you'll be asked to lie still and breathe normally.

Home monitoring

You might have symptoms just once in a while, so a single EKG in the doctor's office may not reveal an abnormal heart rate.

In these cases, you might need to wear a device for longer so doctors can record your heart while you're having symptoms. You may be sent home with one of the following:

  • A Holter monitor is a small, battery-powered EKG that records your heart's activity for 24-48 hours. The device is about the size of a small camera and has little electrodes that are placed on your chest. You can do most of your daily activities, but you shouldn't bathe or shower with it on.
  • An event monitor is also a portable EKG but might be more practical when you have symptoms less than once a day. You can wear it for longer than a Holter. You just press a button on the device when you're having symptoms. The monitor records details only while you feel a fast heartbeat. Your doctor may ask you to wear it for days or weeks.

Further tests

If you're diagnosed based on the results of an EKG, you may need more tests to figure out what type of SVT you have and what's causing it.

Often, this can include what's called an "electrophysiology study" so that doctors can learn how the different sections of your heart are sending electrical signals to each other. For this test, you're sedated at a hospital or clinic and soft, flexible wires are passed through your veins into your heart. You'll need someone to drive you to and from your appointment. Talk to your doctor about how to prepare.

Doctors might also recommend more testing, such as an echocardiogram, an implanted loop recorder, or a stress test. An echocardiogram uses sound waves to create a video of your heartbeat. A doctor implants a loop recorder below the skin of your chest to listen for unusual heart rhythms. During a stress test, you run on a treadmill or take medicine to make your heart speed up. While this happens, the doctor monitors your heartbeat.

Usually, SVT doesn't require any treatment. If it bothers you, your doctor can choose from among several different treatments. They include:

Carotid sinus massage

A carotid sinus massage is when your doctor rubs your neck along your carotid artery, which causes your heart to slow down. Only experienced professionals should do this. Never try it on your own.

Vagal maneuvers

Sometimes, certain actions can relieve SVT. Try coughing, holding your breath, putting an ice pack on your face, or pushing as if you're about to poop. These can calm the vagus nerve, which runs from the lower part of your brain through your neck to your stomach and controls your heart rate. Your doctor can show you how to do these maneuvers safely.

Medications

Some medications can help keep your heartbeat under control. If you regularly have episodes of SVT, your doctor might prescribe:

  • Adenosine (Adenocard)
  • Atropine (AtroPen)
  • Beta-blockers
  • Calcium channel blockers
  • Digoxin (Digitek)
  • Potassium channel blockers

Follow your doctor's directions for taking each medication, and talk with them about potential side effects.

Cardioversion

In an emergency, a doctor can place a set of paddles or patches on your chest to deliver an electric shock to your heart. This helps your heartbeat return to normal.

Catheter ablation

For this treatment, doctors thread tiny tubes (called catheters) through a vein to your heart. These release a pulse of heat or cold that destroys the abnormal electrical pathway that causes SVT.

Pacemaker

In rare cases, a surgeon can put a tiny device called a pacemaker in your chest. When your heart isn't beating normally, this device delivers a small shock to help it return to its regular rhythm.

When you have SVT, it's important to take care of your heart. Make sure to visit your doctor regularly. They can prescribe medications and recommend healthy habits to help manage blood pressure, cholesterol, and other issues that affect your heart.

Some healthy lifestyle habits include:

  • Stick to a heart-healthy diet. Include plenty of fruits, vegetables, and whole grains.
  • Drink enough water. Dehydration can trigger SVT.
  • Exercise. Try walking, swimming, gardening, or other forms of physical activity. Talk with your doctor about finding a routine that's right for you.
  • Don't smoke. Don't be afraid to ask for help with quitting.
  • Find your healthy weight. Talk with your doctor about how to maintain a weight that's right for you.
  • Avoid alcohol. If you drink, do it in moderation: 1-2 drinks a day for most people, depending on your weight and age.
  • Limit coffee or tea. Moderate amounts are usually harmless, but avoid drinking too much.
  • Don't do illegal drugs. Cocaine, methamphetamines, and other drugs can trigger an irregular heartbeat. Talk with your doctor about getting help.
  • Manage stress. Try coping strategies like yoga, meditation, or mindfulness.
  • Get enough sleep. This helps some people to avoid SVT.

Foods to avoid with SVT

Some foods and beverages can trigger SVT episodes and raise your risk of other heart issues. Along with caffeine and alcohol, consider avoiding those that contain a lot of:

  • Salt
  • Saturated fat
  • Sugar
  • Carbohydrates

SVT is usually not life-threatening. But in rare cases, it can make you faint or even cause a cardiac arrest. Eventually, too many bouts of SVT can weaken your heart. That's especially true if you also have other health conditions.

Some SVT treatments, including medications and ablation, can cause side effects. Talk with your doctor about managing these complications.

The best way to avoid SVT is to adopt a heart-healthy lifestyle.

If you already have SVT, try to identify what triggers your irregular heartbeat. Keep a diary of your episodes. Write down your heart rate, symptoms, and activities that might have caused the SVT (such as drinking coffee or smoking a cigarette). Over time, this will help you identify patterns and take steps to avoid these triggers.

If your doctor has prescribed medication for SVT, take it exactly as directed.

If this is your first time having an irregular heartbeat or the episode lasts more than a few seconds, call your doctor.

When should I go to the ER for SVT?

Get medical help immediately if you have sudden chest pain and are short of breath or if you've been diagnosed with SVT and your heart has been racing for 30 minutes or more.

SVT is when you have a fast or an erratic heartbeat. It can be caused by faulty electrical signals in your heart or by stress, exercise, and other triggers. SVT isn't life-threatening, and most people don't need treatment. If you do, you can control it with medication and lifestyle changes.

Is SVT life-threatening?

SVT is rarely life-threatening. But untreated episodes can weaken your heart and could cause heart failure, especially if you already have other medical or heart problems.

When should I be concerned about SVT?

Call 911 if your rapid heartbeat doesn't return to normal after a few minutes. Also call 911 if you have chest pain, trouble breathing, or you feel dizzy or weak.