What Is Supraventricular Tachycardia?

Sometimes, a problem with your heart's electrical signals can make it speed up, even when you're not anxious or exercising. One type of faster-than-normal heartbeat is called supraventricular tachycardia (SVT).

SVT is a group of heart conditions that all have a few things in common.

The term has Latin roots. Supraventricular means “above the ventricles,” which are the lower two sections of your heart. Tachycardia means “fast heart rate.”

Other conditions can cause your heart to beat too fast. Your doctor will need all the details of your symptoms. They’ll also do a physical exam and record your heartbeats to be sure of the diagnosis.

Most of the time, it doesn't cause any serious health problems even though a racing heartbeat can be a scary feeling. Still, you should see your doctor about it. When your heart beats too quickly, it can't pump out enough blood to meet your body's needs.

Sometimes you might have a drop in blood pressure and feel dizzy or lightheaded. Other times, the only feeling is the rapid heartbeat.

Your doctor can try to bring your heart back into a regular rhythm with medicines and other treatments.

How Your Heart Beats

Your heart is a muscular organ that pumps about 100,000 times a day to send oxygen-rich blood out to your body. It has four pumping chambers to do the job. The left and right atria are at the top, and the left and right ventricles are on the bottom.

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

The electrical signal from the SA node makes the muscles of the atria contract to pull blood into the ventricles. Then the signal moves down and causes the muscles of the ventricles to squeeze. That causes blood to go out to the body.

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

The heart normally increases and decreases in speed based on signals that get sent to the SA node. During a bout of SVT, these signals do not occur normally.

Continued

What Is Supraventricular Tachycardia?

Tachycardia is a faster-than-normal heart rate at rest. If you have this condition, your heart beats too quickly -- more than 100 times a minute. The "supra" in supraventricular means above the ventricles.

With this condition, the fast heartbeat starts in the top chambers of the heart, the atria. When electrical signals in the atria fire off early, the atria contract too soon. That interrupts the main electrical signal coming from the SA node. This results in the heart beating very quickly through an abnormal and separate pathway.

This condition is divided into three types:

Atrioventricular nodal reentrant tachycardia is the most common form. If you have it, there’s an extra pathway in your heart that causes an electrical signal to circle around and around instead of moving down to the ventricles. This can trigger the rapid heartbeat.

Atrioventricular reciprocating tachycardia happens when an abnormal pathway links the atria and ventricles, causing the signal to move around and around in a big loop.

If you have the inherited condition called Wolff-Parkinson-White syndrome, you have this extra pathway. This condition is serious. If it is part of your family history, have it checked.

Atrial tachycardia happens when a single short circuit in the right or left atrium triggers a faulty electrical signal.

Bouts of any of these can last from a few seconds to a few hours. When SVT only happens from time to time, it's called paroxysmal supraventricular tachycardia.

Causes

Most of the time, SVT happens without any obvious reason. It often starts when you are in your teens or early 20s.

Sometimes you are born with abnormal pathways or electrical circuits in your heart. Faulty circuits can also form out of scar tissue left behind after surgery.

Your heart is more likely to race if you:

Continued

Symptoms

When your heart beats too quickly, it doesn't have time to fully refill with blood in between beats. That means it can't send enough blood out to your body. That can cause:

Diagnosis

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 the symptoms came on suddenly or slowly
  • What they feel like to you and how long they tend to last
  • Whether you’ve noticed that you’ve had a fast heartbeat after caffeine or stress
  • Whether 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:

EKG test

If your doctor suspects supraventricular tachycardia after hearing about your symptoms, examining you and running some basic tests, they might ask you to get an EKG. You may hear them call it an “electrocardiogram” or an ECG.

This test records your heart’s rhythm over time, so if it’s not beating as it should, it can reveal what the problem is. If you’re getting one, there’s nothing special you need to do ahead of time to get ready.

To set up the test, a nurse or technician will attach six sticky patches 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 put.

Each one will go with a wire that leads to a machine. During the test, which takes just a few minutes, you’ll be asked to lie still and breathe normally.

Continued

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 to 48 hours. The device is about the size of a small camera and has little electrodes placed on your chest while you wear it. You can do most of your daily activities, but you shouldn’t bathe or shower.

An event monitor is also a portable EKG but might be more practical if you have symptoms less than once a day. You can wear it for longer than a Holter and press a button on it when you’re having symptoms. The monitor will record details only for the few minutes you’re feeling the 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 in more detail how the different sections of your heart are sending electrical signals to each other.

For this test, you are sedated at a hospital or clinic and soft, flexible wires are passed through your veins into your heart. You will need someone to drive you to and from your appointment. Talk to your doctor about how to prepare because this test is more involved.

Treatments

One treatment for SVT uses medicine to slow the heartbeat.

If that doesn't fix the problem for you, another option is called ablation. In this procedure, a surgeon burns the pathway that causes the abnormal electrical signals.

If you feel like your heart is fluttering and you have any of the symptoms listed above, make an appointment with your doctor to be tested.

WebMD Medical Reference Reviewed by Suzanne R. Steinbaum, MD on April 14, 2019

Sources

SOURCES:

American Heart Association: "Other Heart Rhythm Disorders," "Tachycardia -- Fast Heart Rate"  “Tachycardia,” “Holter Monitor.”

Boston Medical Center: "Atrioventricular Nodal Reentry Tachycardia (AVNRT)."

Cleveland Clinic: "How Does the Heart Beat."

National Health Service: "Supraventricular tachycardia (SVT) -- Causes."

Stanford: "Atrioventricular Node Re-Entrant Tachycardia (AVNRT)."

Texas Heart Institute: "Categories of Arrhythmias," "Heart Anatomy."

UCLA: "FAQ."

University of Michigan Health System: "Supraventricular Tachycardia (SVT)."

Mayo Clinic: “Tachycardia,”  “Electrocardiogram (ECG or EKG).”

Wang, P. Circulation, “Supraventricular tachycardia,” 2002.

Colucci, R. American Family Physician, “Common Types of Supraventricular Tachycardia: Diagnosis and Management,” Oct. 15, 2010.

NHS Choices: “Supraventricular tachycardia (SVT) -- Diagnosis.”

© 2019 WebMD, LLC. All rights reserved.

Pagination