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Patient Information

Supraventricular Tachycardia (SVT)

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What is Supraventricular Tachycardia?

SVT is a rapid abnormal heart rhythm that begins in the upper chambers of the heart. The atria are above the ventricles, hence the term supraventricular. The term tachycardia refers to a rapid heartbeat of over 100 beats per minute. Supraventricular tachycardia is frequently abbreviated as SVT.

Symptoms you may experience during SVT

• Palpitations

• Light headedness

• Dizziness

• Chest pain

• Shortness of breath

• Loss of consciousness

Typically, patients have varying degrees of symptoms from SVT, but occasionally they may have no symptoms. A common symptom during SVT is palpitations or a sensation that the heart is beating rapidly, fl uttering, or racing. This may last for a few seconds or several hours. Occasionally, you may feel short of breath or feel a pressure or pain in your chest. Sometimes patients will feel light headed or dizzy, and rarely patients will feel like they are about to blackout or faint. Loss of consciousness (also known as syncope) during SVT is a rareoccurrence. Although such symptoms may raise concern, in general the majority of SVTs are not a life-threatening condition. Nonetheless, if any of these symptoms develop, immediate medical attention should be sought.

How is SVT diagnosed?

A heart tracing (ECG) provides a picture of the heart rhythm and is recorded by placing stickers and leads on the chest and limbs. If the patient is experiencing SVT during the ECG, a clear diagnosis can be made. A 24-hour ECG (heart monitor) may be used to record the heart rhythm continuously. This type of monitor is particularly helpful in documenting asymptomatic or very frequent heart rhythm abnormalities. Patients can request a copy of their ECG as per NSF Chapter 8 recommendations. For those patients whose abnormal heart rhythm occurs less frequently an event record (cardio memo) can be used. The patient can keep the cardio memo for a longer period of time (e.g. 1-2 weeks) and activate the recorder when their symptoms occur for a doctor to analyse later.

How can we treat SVT?

Once SVT is diagnosed your doctor and nurse specialist at your local hospital will discuss your treatment options. You may decide if your symptoms are so infrequent to have no treatment for your SVT and your doctor and nurse specialist will advise you if this is an appropriate course of action.

Medications may be used to treat many patients with SVT. Your doctor will discuss with you the most commonly used medications, the benefits and side effects.

A special procedure called catheter ablation is available as an alternative to medication to treat many patients with SVT. This procedure allows the doctor to detect any abnormalities in the electrical system within your heart that has been causing your symptoms; this is called an electrophysiology study. Once the abnormality is found the doctor may then perform a catheter ablation. This aims to cure the abnormal heart rhythm by destroying the area of extra cells which are causing the palpitations.

Your doctor and nurse specialist at your local hospital will give you information on the risks and benefits of this procedure and let you know if it is an appropriate treatment for your medical condition.

What can I do when I develop SVT?

Fast heart rhythms that come on suddenly can often be stopped by performing some simple trick called physiological manoeuvres. These are easy and safe to perform in any setting and may stop the fast rhythm and return the heart to normal. This helps avoid having to go to a hospital casualty department or call an ambulance. You will be given a booklet on physiological manoeuvres to stop SVTs following a talk with a doctor, cardiac physiologist or nurse who has assessed that this is appropriate advice for you.

If when the rhythm starts you feel unwell, for example you have (bad) chest pain, feel very faint or find breathing difficult, call for an ambulance without delay by dialing 999. You may be brought to the casualty department of a local hospital. There, a recording of your heart will be performed and you may be given a drug that is quite effective in stopping the SVT.

It may be useful to keep a record of how frequently your SVT occurs. If you find that your symptoms worsen or the method you use to stop them no longer works, do not worry. Talk to your GP who should be able to recommend a heart rhythm specialist that you can be referred to, to discuss further treatment options.