Supraventricular tachycardia (SVT)

The different types of arrhythmia

          

About supraventricular tachycardia

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.

What happens during supraventricular tachycardia?

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.

Types of supraventricular tachycardia

There are three main types of SVT, which are described below and in the illustration.

  • If the extra pathway is located in your AV node, it’s called atrioventricular nodal re-entrant tachycardia (AVNRT).
  • If the extra pathway connects your atria and ventricles separately from the AV node, it’s called atrioventricular re-entrant tachycardia (AVRT).
  • If the SVT arises from the atrial tissue in an area other than your sinus node, it’s called atrial tachycardia (a less common type of SVT).

Symptoms of supraventricular tachycardia

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:

  • palpitations – you're aware of your heart suddenly beating faster
  • shortness of breath
  • chest pain
  • dizziness and fainting (although this is rare)

These symptoms may be caused by problems other than SVT. If you have any of these symptoms, see your GP for advice.

Complications of supraventricular tachycardia

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.

Causes of supraventricular tachycardia

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:

  • certain medicines
  • problems with your heart since birth (congenital heart disease)
  • emotional or physical stress
  • hormonal changes
  • alcohol
  • caffeine
  • smoking
  • taking illegal drugs, such as cocaine or ecstasy

Diagnosis of supraventricular tachycardia

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:

  • blood tests
  • echocardiogram – an ultrasound scan of your heart that provides a clear image of your heart muscles and valves, and shows how well your heart is working
  • ambulatory ECG – this takes a recording of your heartbeat while you go about your usual daily activities, over 24 hours or longer
  • implantable loop recorder – this is placed under your skin so that it can take a recording of your heartbeat over a much longer period
  • electrophysiological study – this uses electrode catheters to stimulate your heart, allowing your doctor to check your heart's electrical activity in greater detail than an ECG

Treatment of supraventricular tachycardia

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.

Self-help

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.

  • Valsalva manoeuvre. This involves breathing in and then straining out (as if having a bowel movement) while holding your breath – sit or lie down first because this could cause you to faint.
  • Diving reflex. Fully immerse your face in cold water or suck on ice cubes.
  • Change position. Bend over or lie down.
  • Hold your breath or cough.

Your doctor may suggest you improve your heart health by:

  • reducing your alcohol and caffeine intake
  • stopping smoking, if you smoke
  • doing 150 minutes (two and a half hours) of moderate exercise a week in bouts of 10 minutes or more

Physical therapies

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

Emergency treatments for SVT include:

  • electrical (DC) cardioversion – this uses an electric shock to restore your rapid heartbeat back to normal
  • medicines given through a drip into your bloodstream, such as adenosine and verapamil

Medicines

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

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.

What is Wolff-Parkinson-White syndrome and how would I know if I have it?

Answer

Wolff-Parkinson-White syndrome is caused by an unusual connection between your atria and your ventricles (the upper and lower chambers of your heart). This puts you at risk of having supraventricular tachycardia (SVT) and atrial fibrillation. You may have no symptoms and not know that you have this syndrome until you have an electrocardiogram (ECG) carried out.

Explanation

If you have Wolff-Parkinson-White syndrome, it’s because the upper and lower chambers of your heart didn’t separate properly during your development before you were born. This leads to an unusual connection forming between your atria and ventricles, called an accessory pathway.

In your heart, when it’s functioning normally, electrical impulses only travel in one direction, from your upper to your lower chambers, through an area called the atrioventricular (AV) node. However, if you have Wolff-Parkinson-White syndrome, the accessory pathway creates a circuit, allowing the impulses to travel back up to your atria and activate the muscles before the next heartbeat. This can cause symptoms of SVT.

However, you may not even know you have Wolff-Parkinson-White syndrome unless this shows up on an ECG. You will most likely be treated for Wolff-Parkinson-White with a procedure called catheter ablation. 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. You doctor may also prescribe you antiarrhythmic medicines.

If you have Wolff-Parkinson-White syndrome, your doctor will be able to discuss which treatment options are most suitable for you.

How long does it take to recover from catheter ablation for supraventricular tachycardia?

Answer

Most people recover quickly from catheter ablation, usually within a day or two after having the procedure.

Explanation

Catheter ablation is a minimally invasive procedure, which means it involves making only a small puncture in your groin. You have the procedure done under local anaesthesia and sedation. The anaesthetic completely blocks pain from your groin area and the sedative helps you to feel relaxed during the procedure, without putting you to sleep. You should be able to go home on the same day as the procedure or the day after.

You may feel pains on and off in your chest, shoulders or neck during the first few weeks after the procedure. These are caused by the scarring process.

You will usually need to take it easy for a few days after the procedure. You shouldn’t drive for two days after the procedure or lift anything heavy for at least two weeks.

Catheter ablation is a complex procedure and you may need a repeat procedure to successfully treat your symptoms.

What is sinus tachycardia and how does it relate to supraventricular tachycardia?

Answer

Sinus tachycardia means your heart is beating in a normal, regular rhythm, but faster than usual. It's not related to supraventricular tachycardia because it’s a normal response to changes in your body and isn’t usually caused by a problem with electrical signals in your heart.

Explanation

Your heart beats faster than normal in response to your environment or situation. Your heart rate will speed up when you:

  • increase your physical activity
  • feel fear or panic
  • have a fever
  • are pregnant
  • take certain medicines, including anticancer treatments
  • take some types of illegal drugs (such as amphetamines)
  • have caffeine or alcohol (especially in larger quantities than usual)
  • smoke

Some medical conditions, such as an overactive thyroid gland (hyperthyroidism), severe anaemia or pulmonary embolism, can also cause your heart rate to be higher than is normal for you. However, these reasons for a faster heart rate are less common and you will usually have other symptoms too.

Most people don't need treatment for sinus tachycardia because their heartbeat doesn’t stay raised for long and returns to normal after the stimulus has been removed. However, if it's caused by an underlying condition, then your GP will be able to advise you about treatments.

Inappropriate sinus tachycardia is when your heart beats faster than usual for no apparent reason. This may be due to an abnormal sensitivity to natural hormones that are present in your body, such as adrenaline. It might also be associated with an anxiety disorder. It’s important that your GP rules out all causes of sinus tachycardia, but there might be no apparent cause.

If you’re concerned about your heart rate, or have other symptoms, such as chest pain or dizziness, see your GP.