Supraventricular tachycardia (SVT) is when your heart beats too fast, usually at a rate of about 130 to 250 beats per minute. SVT is a type of arrhythmia (abnormal heart rhythm). It’s caused by faulty electrical signals in your heart and often affects young, healthy people.
Tachycardia means a rapid heart rate of more than 100 beats per minute. Supraventricular means that the problem starts in the upper part of your heart (above the ventricles).
SVT episodes are often temporary and frequently go away on their own without any treatment. They often happen in young, healthy people. Episodes often become less frequent as you get older, but you may find they get worse. Episodes vary in how long they last, from a few seconds or minutes, or up to several hours.
Your heartbeat is controlled by electrical signals (impulses), which start in a part of your heart’s muscular wall, called the sinus node, and travel through your heart making it contract. The signals travel from the atria (the upper chambers of your heart) to the ventricles (the lower chambers of your heart) through an area called the atrioventricular (AV) node. The AV node helps to synchronise the pumping action of the atria and ventricles.
SVT most often occurs when there is an extra electrical pathway in your heart between your atria and your ventricles. This allows electrical signals to 'short-circuit' and re-enter the atria. The signals end up travelling around your heart in a circle. These types of SVT are referred to as re-entrant tachycardias or paroxysmal SVT. This means symptoms come on suddenly and are temporary.
There are three main types of SVT, which are described below and in the illustration.
You may or may not have symptoms of SVT. You’re more likely to have symptoms if you already have heart disease.
The symptoms you experience during an attack of SVT may include:
These symptoms may be caused by problems other than SVT. If you have any of these symptoms, see your GP for advice.
Your heart may not be able to pump blood effectively around your body because your heart rate is abnormal. This can result in low blood pressure, which may cause fainting. Low blood pressure may also result in less blood flowing to your heart (ischaemia), which can damage your heart muscle, causing your heart to pump less effectively. This may result in heart failure. These complications are more common if you have other problems with your heart, such as valve disease.
You also have a small risk of sudden death, but usually only if you have a particular type of SVT called Wolff-Parkinson-White syndrome. See our frequently asked questions for further information.
The cause of SVT isn't fully understood at present. Episodes often come on without warning and you may develop SVT without having any underlying cause or risk factor. However, certain factors may lead to SVT developing, including:
Your GP will ask about your symptoms and examine you. He or she will check your blood pressure, listen to your heartbeat and take your pulse. You’re likely to have a test called an electrocardiogram (ECG). An ECG records the electrical activity of your heart to see what your heart rhythm is.
If your GP suspects that you have SVT, he or she may refer you to a cardiologist, a doctor specialising in heart conditions. You may have other tests in hospital, including:
There are many treatments available for SVT. Your treatment will depend on your symptoms. Your doctor will discuss your treatment options with you.
The aim of treatment is to control your heart rhythm and rate, and reduce your risk of heart failure. You may not need any treatment at all, especially if your symptoms are mild.
Your doctor may advise you on things you can do to stop an episode. You can try any of the options below when you feel an SVT episode starting.
Your doctor may suggest you improve your heart health by:
Applying pressure to an artery in your neck may help to stop your heart beating rapidly. However, this must only be done by a doctor. It can be dangerous to do on some people and your doctor will need to check whether you're suitable for this technique.
Emergency treatments for SVT include:
If your symptoms come on suddenly, you may be given antiarrhythmic medicines, either as tablets or given through a drip into your bloodstream, to try to get your heart rhythm back to normal (this is called pharmacological or medical cardioversion). This is usually tried within 48 hours of having symptoms. If this type of medicine is not successful, you may have DC cardioversion to restore your normal heart rate.
There are several different types of medicine that can help control your heart rate and rhythm, including beta-blockers, calcium-channel blockers and antiarrhythmic medicines. You often take them to prevent further SVT attacks.
Always ask your doctor for advice and read the patient information leaflet that comes with your medicine.
Surgery is only used when your symptoms haven't responded very well to other treatments. Your doctor may advise you to have a procedure called catheter ablation if your attacks require regular medication. Small tubes called electrode catheters are passed into the veins in your groin and threaded up to your heart. Any tissue that is disrupting or causing abnormal electrical signals in your heart is burnt or frozen to destroy it.
Produced by Alice Rossiter, Bupa Health Information Team, August 2012.
For answers to frequently asked questions on this topic, see FAQs.
For sources and links to further information, see Resources.
This information was published by Bupa's Health Information Team and is based on reputable sources of medical evidence. It has been reviewed by appropriate medical or clinical professionals. Photos are only for illustrative purposes and do not reflect every presentation of a condition. The content is intended only for general information and does not replace the need for personal advice from a qualified health professional. For more details on how we produce our content and its sources, visit the about our health information page.
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