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. You might hear your doctor call it SVT.

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.

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.

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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:

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:

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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 August 15, 2016

Sources

SOURCES:

American Heart Association: "Other Heart Rhythm Disorders," "Tachycardia -- Fast Heart Rate."

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)."

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