Supraventricular tachycardia, also known as SVT, is a common abnormal heart rhythm that can affect all ages. When you have SVT, the electrical system in your heart isn’t working right. You might experience a sudden rapid heartbeat, which can lead to shortness of breath, chest pain and, in rare cases, loss of consciousness.

SVT often ends suddenly. It stops either on its own or when you take an action to slow your heart rate. These are called vagal maneuvers and include gagging or coughing. In some cases, you might need medication injected into a vein by emergency medical services or when you are in the ER.

While there are some known triggers for SVT, such as caffeine, stress and exercise, often an episode has no clear triggers. For example, SVT could occur while you are relaxed watching TV or it could wake you up from sleep.

After the first episode of SVT, sometimes no treatment is needed. The next attack could occur several years down the road and might not justify taking medication every day. When patients experience more than one episode, medicines could help reduce the number of times they occur. The most commonly used medications are beta-blockers and calcium channel blockers. Other medications such as anti-arrhythmic drugs also could be used. But sometimes medications are not that effective, and you could still experience SVT.

Another treatment option for SVT is to have an ablation. Ablation is a procedure that is usually done while you are sedated but still conscious. The goal is to find the tissue causing the rapid heartbeat and destroy it (burn). This procedure doesn’t require a long stay in the hospital, has a high success rate, and a low complication rate. It can be considered as first-line therapy for SVT because it can cure SVT and remove the need for medical therapy. Talk with your health care professional about the treatment options, risks and benefits to decide what is right for you.

There are different forms of supraventricular tachycardia (SVT), an abnormal fast heart rhythm. At times, thyroid disease, caffeine, medications with stimulants, or stress can cause an episode of SVT. However, often no trigger is identified.

Remember that your heart has a system of electrical impulses that helps control the rhythm and number of times your heart beats per minute. The electrical signals travel along “pathways.” Some types of SVT involve a faulty electrical pathway. Examples include:

Atrioventricular Nodal Reentrant Tachycardia (AVNRT): With AVNRT, the most common form of supraventricular tachycardia, there is a slow pathway in the middle of the heart. An extra beat timed just right sets off a circuit by going down the slow pathway and then going up a fast pathway. This loops around many times and creates a fast heart rate.

Wolff-Parkinson-White syndrome (WPW): With WPW, there is an extra pathway between the upper and bottom chambers of the heart. A circuit can be created with an extra beat going down the normal path and then up this extra pathway. It can go backward as well. Either way, this loops around many times creating a fast heart rate.

Atrial Tachycardia (AT): With atrial tachycardia, a cluster of cells in the upper chamber of the heart fires away, creating a rapid heartbeat.

Signs and symptoms

With SVT, your heart beats very fast for reasons other than stress or exercise. Often, you will notice a sudden increase in your heart rate ( > 100 beats per minute and even rates of > 200 beats per minute). Then, it suddenly returns to normal (about 60-100 beats per minute).

Depending on how fast the heart is beating, the symptoms can include:

• Palpitations
• Lightheadedness
• Passing out
• Sweating
• Chest pain
• Shortness of breath

Supraventricular tachycardia (SVT) can happen to anyone. If you have an episode of SVT, the problem with your heart’s electrical system can be temporary and triggered by several factors. Examples include:

• Drinking too much caffeine or alcohol (energy drinks with high caffeine levels are a common cause)
• Smoking
• Untreated thyroid disorders
• Going through psychological and physical stress
• Using illegal drugs
• Having family members who have a history of rapid heart rate (tachycardia)

In addition, certain conditions can increase your risk of developing SVT:

• Congenital heart defect or prior heart surgery
• Anemia
• Chronic respiratory illness
• Abnormally high thyroid function (hyperactive thyroid)
• Coronary heart disease
• Certain cardiac medications

Some other medications, such as digoxin or antihistamines, can increase risks of developing SVT, too.

When to Call a Doctor

Generally, SVT is not life-threatening. Sometimes, SVT does not cause any symptoms, and you may not need any treatment. However, you should talk to your health care professional or go to the emergency room if you have any concerning symptoms. Those include:

• Dizziness
• Lightheadedness
• Fainting (syncope) or near fainting
• Chest pain

Techniques called “vagal maneuvers” can help slow down or stop an episode of SVT. Some examples of these maneuvers:

• Exhaling strongly through a small tube or closed airway
• Coughing or gagging
• Putting your face into ice-cold water
• Holding your breath and bearing down (Valsalva maneuver)

If these steps fail to end or slow down your rapid heart rate, you should talk to your health care professional or go to an emergency department.

To find out whether you have supraventricular tachycardia (SVT), your health care professional will ask you questions about your symptoms and do a physical exam. These questions might include:

• What, if anything, triggers your fast heart rate (exercise, stress, caffeine)?
• What symptoms do you feel? Do they come on slowly or quickly? How long do they last?
• Do your heartbeats feel regular or uneven?
• Does anyone in your family have heart problems?

During the physical exam, your health care professional will listen to your heart and lungs. He or she will also feel your thyroid gland on your neck. Other tests may include blood tests and an echocardiogram (an ultrasound that shows pictures of the heart in motion).

Your health care professional will do a test called an electrocardiogram (ECG). During an ECG, sticky patches (electrodes) are placed on your chest. Each electrode has a wire that goes to the ECG machine so it can record your heart’s electrical activity over several minutes. If you are in SVT, the machine will be able to measure it.

If you do not have an episode of SVT during your health visit, you may be given an electrocardiogram that you can wear at home. You may be asked to wear:

• A Holter monitor. This is a small ECG that records your heart’s electrical activity for 24 hours.
• An event monitor. You can wear this for longer than a Holter monitor and press a button when you feel symptoms. The monitor will record details for the next few minutes while you’re feeling the fast heart rate. You may be asked to wear this for days or weeks depending on how frequently you have symptoms.

If you’re ECG shows SVT, your health care professional may want to perform an electrophysiology study to determine what type of SVT you have and what is causing it. This test is performed in the hospital. You will be sedated and wires are passed through your veins into your heart. Your doctor can look at different sections of your heart and see how they are sending electrical signals.

In most cases, if you experience short episodes of supraventricular tachycardia (SVT) with no symptoms, your health care professional may recommend no therapy. However, if you do have symptoms, frequent episodes, or both, then you will likely require treatment.

Common symptoms are palpations, dizziness, chest pain, and feeling like you are about to faint. Treatment for SVT includes drug therapies and catheter ablation. What type of therapy is best for you depends on the type of SVT you have, how often it occurs, and the degree and length of symptoms. The goal is to prevent these abnormal heart rhythms and to limit your symptoms.

Sudden, Short Episode of SVT

The initial treatment for a sudden episode of SVT is vagal maneuvers, such as bearing down, coughing, or holding your breath. These actions can slow the electrical impulses in your heart and may stop the SVT. Sometimes, your health care professional also may prescribe medications such as beta-blockers to be taken as needed during these sudden, short episodes.

If the SVT episode continues, you should go to the emergency room. There, you might be given a medicine called adenosine, which also slows the electrical impulses in the heart, or another medicine called verapamil. In rare cases, you might require an electrical shock to get your heart back into a normal rhythm.

Long-Term SVT Treatment

You and your health care team will consider many factors — including your values and the type of SVT you have — when deciding what treatment is right for you. You should be actively involved in making the decision between medical therapy and ablation therapy. Each type of SVT responds differently to medical therapy, and has different risks and success rates with ablation. Also, the risk of side effects from drug therapy should be weighed against the risks and benefits of ablation.

Drug Therapy: Patients are prescribed daily medications to help prevent SVT episodes from occurring or to slow heart rates during SVT episodes. Commonly prescribed medications are beta-blockers, verapamil, and digoxin. Occasionally, other medications called antiarrhythmic drugs (such as amiodarone or sotalol) may be given to prevent SVT episodes from occurring.

Ablation Therapy: Ablation can be considered as a primary, first-line therapy for certain types of SVT, and it may also be considered if you often have symptoms with medical therapy. During an ablation, a small tube called a catheter is placed through a vein typically in your leg, then guided to your heart. An electrical study is done to find the area in your heart causing the electrical problems that trigger SVT. Your doctor then destroys this area either by burning or freezing that part of the heart.

Ablation is very successful in treating specific forms of SVT. However, ablation therapy does have some rare, but serious procedural risks. Be sure to talk about the procedure and its risks with your physician. Together with your health care team, you will find a treatment that is right for you.

The occurrence of supraventricular tachycardia (SVT) can be unpredictable. Sometimes, caffeine or exercise could trigger an SVT episode, but often it’s not possible to predict when one will happen.

In general, SVT is not a life-threatening condition. Therefore, try not to allow a history of SVT to affect your quality of life.

However, if episodes of SVT happen frequently, you should talk with your health care provider about procedures, such as ablation or medical therapy, that might be able to cure the abnormal heart rhythm.

Prevention

One way to prevent SVT is to avoid substances that may cause the abnormal heart rhythm. These are commonly called triggers. Some common triggers include:

• Alcohol
• Cigarettes
• Caffeine
• Illegal drugs (cocaine, methamphetamine)
• Herbal supplements

You may be prescribed medications to prevent episodes of SVT. Remember to bring a list of all your medications to your appointments. In addition, don’t use any medications or supplements without talking to your health care professional.

It’s also important to keep up with regular health visits. If your symptoms get worse, or if you notice anything new, be sure to share those details with your health care team.

If you’ve been diagnosed with supraventricular tachycardia, there are several key questions that you should ask your cardiologist during your next visit. These questions will ensure that you and your doctor have discussed your major risk factors so that you can become or stay as healthy as possible.

• What is supraventricular tachycardia (SVT)?
• What causes supraventricular tachycardia (SVT)?
• What are the symptoms of supraventricular tachycardia (SVT)?
• How is supraventricular tachycardia (SVT) diagnosed?
• How common is supraventricular tachycardia (SVT)?
• Does supraventricular tachycardia (SVT) always require treatment?
• What are the treatment options for supraventricular tachycardia (SVT)?
• What medications are used for supraventricular tachycardia (SVT) and what are the side effects I should watch for?
• What are the risks of supraventricular tachycardia (SVT) if left untreated?
• Does supraventricular tachycardia (SVT) increase my risk of cardiac arrest?
• What is an electrophysiologist and when should I see them in addition to my general cardiologist?
• How often should I follow up with my cardiologist or primary cared doctor about supraventricular tachycardia (SVT)?
• Can supraventricular tachycardia (SVT) be prevented?
• Is supraventricular tachycardia (SVT) hereditary?