Supraventricular Tachycardia

What is supraventricular tachycardia?

Supraventricular tachycardias (SVT) are a group of abnormally fast heart rhythms. Normally, a special group of cells begin the electrical signal to start your heartbeat. These cells are in the sinoatrial (SA) node. This node is in the upper right chamber of your heart (right atrium). The signal quickly travels down your heart’s conducting system to the two lower chambers of your heart (ventricles). Along the way, the signal moves through the atrioventricular (AV) node, a special group of cells 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 in a coordinated way.

In SVT, the signal to start your heartbeat doesn’t come from the SA node the way it should. Instead, it comes from another part of the left or right atrium, or from the AV node. It is called "supraventricular" because the signal begins someplace above your ventricles. An area outside the SA node begins to fire quickly, causing a rapid heartbeat of over 100 beats per minute. This shortens the time your ventricles have to fill. If your heartbeat is fast enough, your heart may not be able to pump enough blood forward 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 SVTs. The most common type in adults is atrioventricular nodal reentrant tachycardia (AVNRT). This occurs when you have two channels through the AV node, instead of just one. The electricity can get into a looping circuit with signals going down one channel and up the other. It can occur at any age, but it most often starts in young adulthood. It is slightly more common in women.

Another common type of SVT is atrioventricular reciprocating tachycardia (AVRT). In this condition, you are born with an extra electrical connection between the atrium and the ventricle (known as an accessory pathway) that can conduct electricity. This condition allows your heart to get caught up in a looping electrical circuit. The electricity either goes down the AV node and returns back to the atrium through the accessory pathway (called orthodromic). Or the reverse occurs with the signal traveling down the accessory pathway and returning through the AV node (called antidromic) This circuit continues until it is interrupted and the tachycardia stops. This type of SVT is slightly more common in younger women and children.

Atrial tachycardia is another common type of SVT. In this case, a small group of cells in the atria begin to fire abnormally, triggering the fast heartbeat. Multifocal atrial tachycardia is a related type. In this case, multiple groups of cells in your atria fire abnormally. 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, SVTs are somewhat uncommon. But they are not rare. Atrial fibrillation and atrial flutter are also technically types of SVT but these are usually separated into their own category because they are associated with other risks, can last for days or even years, and have a different mechanism

What causes supraventricular tachycardia?

SVT is usually a result of faulty electrical signaling in your heart. It is commonly brought on by premature beats. Some types of SVT run in families, so genes may play a role. Other types may be caused by lung problems. It can also be linked to a number of lifestyle habits or medical problems. Some of these include:

  • Excess caffeine or alcohol

  • Heavy smoking

  • Certain medicines

  • Heart attack

  • Mitral valve disease

What are the symptoms of supraventricular tachycardia?

You may not have any symptoms if you have SVT. Symptoms may vary based on how long the tachycardia lasts and how fast the heart rate is. Common symptoms include:

  • Chest discomfort

  • Shortness of breath

  • Fatigue

  • Lightheadedness or dizziness

  • Pulsations in the neck

  • Unpleasant awareness of the heartbeat (palpitations)

Fainting, more severe chest pain, and nausea are less common symptoms. Very rarely can SVT cause sudden death.

How is supraventricular tachycardia diagnosed?

Diagnosis starts with a medical history and physical exam. Your healthcare provider will also use tests to help diagnose SVT. These tests will help your provider identify the type of SVT you have. They also help your provider check for possible underlying causes and complications. Tests might include:

  • Electrocardiogram (ECG), the most important initial test to analyze the abnormal rhythm

  • Continuous electrocardiogram, to watch your heart rhythm over a longer period

  • Blood work, to test for various causes

  • Chest X-ray, to check for lung problems and examine the size of your heart

  • Exercise stress test, to see how your heart works during exercise

  • Echocardiography, to check your heart structure and function

  • Electrophysiologic study (EPS), to evaluate the electrical activity and pathways in your heart

Your primary healthcare provider might first diagnose your SVT. But they will likely send you to a heart doctor (cardiologist).

How is supraventricular tachycardia treated?

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

  • Maneuvers to stop SVT

  • Medicines to stop SVT, like calcium channel blockers, beta blockers or adenosine

  • Electrocardioversion. This sends a shock to the heart to get it back to a normal rhythm.

  • Catheter ablation

Maneuvers are usually the first treatment unless you have severe symptoms. These attempt to activate a nerve called the vagus nerve. Activating this nerve can cause a brief slowing of your heartbeat in attempt to break the abnormal circuit. Your healthcare provider might have you do a Valsalva maneuver (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, having you blow in a straw, or cough hard. Each of these techniques can sometimes bring you out of SVT. If they don’t, your provider might give you medicines. If your symptoms are severe or your condition is unstable, you will usually have electrocardioversion as the first treatment. .

Long-term treatment depends on the type of SVT and the intensity of symptoms. You may not need any treatment for SVT if you have only had one episode or the episodes are very rare, , especially if SVT went away with maneuvers alone. In some cases, your healthcare provider may prescribe medicines to stop SVT that you will need to take only as needed. Beta-blockers or calcium channel blockers 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 your SVT is more frequent, you may need to take medicine every day. Some people may need to take several medicines to prevent episodes of SVT.

Catheter ablation is now often a suggested treatment for recurring SVT. In some cases, it may be the initial recommended treatment. Ablation can often cure SVT. The procedure involves placing a small catheter through a blood vessel in the groin and threaded into your heart. Your healthcare provider then performs a small burn or small freeze on the abnormal area of your heart that is causing the fast heart rhythm. Ask your healthcare provider about what treatment strategy is right for you.

How is supraventricular tachycardia managed?

Your healthcare provider might make other recommendations to manage your SVT. These might include:

  • Cutting back on alcohol and caffeine

  • Avoiding smoking

  • Reducing stress

  • Eating a heart-healthy diet