Supraventricular Tachycardia

What is supraventricular tachycardia?

Supraventricular tachycardias (SVT) is a fast heart rhythm (heartbeat) that's not normal. It's a problem in the electrical system of the heart. The word supraventricular means above the two lower heart chambers (ventricles). With SVT, the abnormal rhythm starts in the upper heart chambers (atria). This condition is also called paroxysmal supraventricular tachycardia. The fast heart rhythms may start and stop suddenly. They can also occur with intervals of normal heart rhythm.

A normal heartbeat is triggered by an electrical signal that begins in a special group of cells. These cells are in the sinoatrial (SA) node. This node is in the right atrium, the upper right chamber of your heart. In an adult, it sends out a regular electrical pulse 60 to 100 times a minute. The signal quickly travels down your heart’s conducting system to the ventricles. Along the way, the signal moves through the atrioventricular (AV) node. This is located between your atria and your ventricles. From there, the signal travels to your left and right ventricle. As it travels, the signal triggers nearby parts of your heart to contract. This helps your heart pump the way it's supposed to.

When you have SVT, the signal to start your heartbeat doesn’t come from the SA node. Instead, it comes from another part of the left or right atrium, or from the AV node. An area outside the SA node begins to fire quickly. This causes a rapid heartbeat of over 100 beats a minute. It gives your ventricles less time to fill with blood before pumping it out. If your heartbeat is too fast, your heart may not be able to pump enough blood out to the rest of your body. The abnormal heart rhythm may last for a few seconds to a few hours before your heart returns to its normal rhythm.

There are several types of SVT:

• Atrioventricular nodal reentrant tachycardia (AVNRT). This is the most common type in adults. It occurs when you have two channels or pathways through the AV node, instead of just one. The electrical signal can get into a looping circuit. Signals going down one channel and up the other. It can occur at any age. But it most often starts in young adulthood. It's a bit more common in women.

• Atrioventricular reciprocating tachycardia (AVRT). This is another common type of SVT. You're born with an extra electrical connection between the atrium and the ventricle. This is called an accessory pathway. This type lets your heart get caught up in a looping electrical circuit. The signal goes down the AV node and then comes back to the atrium through the accessory pathway. Or it goes the other way: It travels down the accessory pathway and comes back through the AV node. It keeps going until it's interrupted and the fast heartbeat stops. This type of SVT is slightly more common in younger women and children. It's also called Wolff-Parkinson-White (WPW) syndrome.

• Atrial tachycardia. This is a common type of SVT. A small group of cells in the atria start to fire in a way that's not normal. This triggers the fast heartbeat. Multifocal atrial tachycardia is a related type. In this case, many groups of cells in your atria fire in a way that's not normal. These types of SVT happen more often in middle-aged people. Multifocal atrial tachycardia is more common in people with heart failure or other heart or lung diseases.

In general, SVT is not very common. But it's not rare. Atrial fibrillation and atrial flutter are also types of SVT. But they are often put into their own category because they are linked with other risks. They can also last for days or even years and have a different mechanism.

What causes SVT?

SVT is often caused by faulty electrical signaling in your heart. It often begins with beats that happen too soon. Some types of SVT run in families. Other types may be caused by lung problems. It can also be linked to some lifestyle habits or health problems. Some of these include:

• Too much caffeine or alcohol.

• Heavy smoking.

• Certain medicines.

• Heart attack.

• Mitral valve disease.

What are the symptoms of SVT?

Symptoms may vary based on how fast the heart rate is and how long it lasts. Some people with SVT have no symptoms. If you have symptoms, they may include:

• Chest discomfort.

• Shortness of breath.

• Fatigue.

• Feeling lightheaded or dizzy.

• Pulsations in the neck.

• Unpleasant awareness of the heartbeat (palpitations).

Fainting, worse chest pain, and nausea are less common symptoms. In rare cases, SVT can cause sudden death.

How is SVT diagnosed?

Diagnosis starts with a health history and physical exam. Your health care provider will also do tests to help diagnose SVT and know what type of SVT you have. And they will check for other health problems that could cause SVT. Tests might include:

• Electrocardiogram (ECG). This checks for an abnormal heartbeat. It is the most important first test.

• Continuous electrocardiogram. This watches your heart rhythm over a longer period.

• Blood tests.

• Chest X-ray. This may be done to check for lung problems and look at the size of your heart.

• Exercise stress test. This checks how well your heart works during exercise.

• Echocardiography. This checks your heart structure and function.

• Electrophysiologic study (EPS). This checks the electrical activity and pathways in your heart.

Your primary provider might be the first to diagnose your SVT. But they'll likely send you to a heart specialist (cardiologist).

How is SVT treated?

SVT needs short-term and long-term treatment. Options for short-term treatment include:

• Maneuvers to stop SVT. These are often the first treatment unless you have severe symptoms. They are an attempt to activate a nerve called the vagus nerve. Activating the nerve can briefly slow your heartbeat. This can break the abnormal circuit in the heart. Your health care provider might have you do a Valsalva maneuver. With this, you bear down with your stomach muscles as though you were trying to have a bowel movement. Your provider might also try massaging the carotid artery in your neck. Or they may have you try blowing in a straw or coughing hard.

• Medicines. These can be used to stop SVT if maneuvers don't work well enough. They include calcium channel blockers, beta blockers, and adenosine.

• Electrocardioversion. This sends a shock to the heart to get it back to a normal rhythm. If your symptoms are severe or your condition is unstable, you will often have this as the first treatment.

Long-term treatment depends on the type of SVT and how bad the symptoms are. You may not need any treatment for SVT if you have had only one episode or the episodes are very rare. Options for long-term treatment include:

• Medicines to prevent SVT. Your provider may have you take them only as needed. Calcium channel blockers, beta blockers, or antiarrhythmic medicines are common choices. This may be an option for you if you have fewer than 3 episodes of SVT per year. But the medicines may often take 15 to 30 minutes to take effect. If you have SVT more often, you may need to take medicine every day. Some people may need to take several medicines to prevent episodes of SVT.

• Catheter ablation. This is the preferred treatment for SVT that keeps happening. In some cases, it may be the first treatment. It can often cure SVT. In this procedure, a small catheter is placed through a blood vessel in the groin and threaded to your heart. Your provider then makes a small burn or small freeze on the part of your heart that is causing the problem.

Ask your provider about what treatment option is right for you.

How is SVT managed?

Your health care provider might recommend other ways to manage your SVT. These include:

• Cutting back on alcohol and caffeine.

• Quitting smoking.

• Reducing stress.

• Eating a heart-healthy diet.

When should you contact your doctor?

Contact your health care provider if you have severe symptoms. This includes palpitations, lightheadedness, chest pain, or sudden shortness of breath. If your symptoms are getting worse or more frequent, see your provider as soon as possible.

Key points about SVT

• SVT is a type of abnormal heart rhythm. Something signals a part outside of the SA node to fire much faster than it should. Or something triggers the signal to follow a looping circuit. This results in a fast heartbeat that can last anywhere from a few seconds to several hours.

• There are several types of SVT. Your treatment options may vary based on what subtype you have.

• In very rare cases, SVT can cause sudden death.

• You might need a shock to the heart if you are having severe symptoms from SVT.

• Some people with SVT need to take medicines only when an episode of SVT happens. Others need to take medicine all the time. Ablation is often a good option for many people.

• It is important to follow your health care provider’s instructions about medicine and your lifestyle.

Next steps

Tips to help you get the most from a visit to your health care provider:

• Know the reason for your visit and what you want to happen.

• Before your visit, write down questions you want answered.

• Bring someone with you to help you ask questions and remember what your provider tells you.

• At the visit, write down the name of a new diagnosis. Note any new medicines, treatments, or tests. Also write down any new instructions your provider gives you.

• Know why you're getting a new medicine or treatment and how it will help you. Also know what the side effects are.

• Ask if your condition can be treated in other ways.

• Know why a test or procedure is advised and what the results could mean.

• Know what to expect if you don't take the medicine or have the test or procedure.

• If you have a follow-up visit, write down the date, time, and purpose for that visit.

• Know how you can contact your provider if you have questions.