Supraventricular tachycardia (SVT)

Supraventricular tachycardia (SVT) is a type of abnormal heartbeat (arrhythmia) in which your heart beats too fast. It’s caused by faulty electrical signals that start in an area of your heart above your ventricles (the lower chambers of your heart). 

SVT can affect people of all ages. It’s not uncommon to get it if you’re young and otherwise healthy.

What happens in supraventricular tachycardia?

Your heartbeat is controlled by electrical signals (impulses) that travel through your heart and make it contract.

Supraventricular tachycardia (SVT) is a term for when your heart beats faster than normal because of a problem that happens above your ventricles. Your ventricles are the lower chambers of your heart. There are different types of SVT. It’s often caused by an extra electrical pathway (or pathways) in your heart between your atria (the top chambers of your heart) and your ventricles. This can cause the electrical signals to form a short circuit in your heart, making it beat faster than it should. 

Watch our animation to see how your heart beats normally and what happens in SVT.

With SVT, you usually get episodes where your heart suddenly starts beating faster. These can last anything from a few seconds to several hours or, rarely, more than 12 hours before going back to normal. During an episode of SVT, your heart may beat between 140 to 250 beats per minute. Normally, it beats between 60 and 100 times a minute (when you’re resting).

Symptoms of supraventricular tachycardia

Supraventricular tachycardia (SVT) doesn't always cause symptoms – it depends on several factors, including how long the episode of SVT lasts, and how fast your heart rate is.

During an episode of SVT, you may:

• get palpitations (when you can sense your heart thumping, fluttering or skipping beats)
• have pounding in your neck
• feel lightheaded and dizzy
• feel short of breath
• have chest pain or discomfort
• pass out (but this isn’t common)

If you get any of these symptoms and they’re relatively mild, go and see your Doctor. If you need urgent medical care, go to your nearest accident and emergency department.

More serious problems are rare with SVT, but may be possible with a particular type of SVT called Wolff–Parkinson–White Syndrome. For more information, see our FAQ: What is Wolff–Parkinson–White syndrome?

Diagnosis of supraventricular tachycardia

Your Doctor will ask about your symptoms and examine you. Your Doctor will want to know how often you’ve been having symptoms, what they feel like and if anything in particular seems to set them off. They’ll check your blood pressure, listen to your heartbeat and take your pulse. Your Doctor will also ask about your medical history.

You’ll need to have a test called an electrocardiogram (ECG). An ECG records the electrical activity in your heart. You may need to have an ambulatory ECG, which records your heartbeat while you go about your usual activities over 24 hours or more. Or you might need to have an implantable loop recorder. This is a small device which is implanted under your skin and is programmed to record abnormal rhythms.

Your Doctor may also arrange for you to have some of the following tests.

• Blood tests. These will check for substances that may be causing SVT, and for other conditions that may be causing your symptoms.
• Exercise ECG (cardiac stress test). This is when you have an ECG while you exercise on a treadmill to see if this triggers an arrhythmia. 
• Chest X-ray. This will allow your doctor to look for any changes in your heart or lungs that might be causing the problem. 
• Echocardiogram. This test uses ultrasound to provide a clear image of your heart muscles and valves and can show how well your heart is working.

It can be useful if you’re able to measure your own pulse because it can help your doctor to see what happens when you have an attack. Devices such as smart watches and phones may also be able to help you monitor your symptoms. Talk to your doctor about how you may be able to use these.

Treatment of supraventricular tachycardia

Treatment for supraventricular tachycardia (SVT) is aimed at stopping attacks and controlling your heart rhythm and rate to prevent further attacks. What treatment you’re offered will depend on the type of SVT you have, how often you get symptoms, how severe they are and how long they last. Your doctor will discuss your treatment options with you.

Stopping an attack

If you see a doctor while you’re having symptoms of SVT, they may need to give you treatment to stop the attack. This may include one of the following options. 

• Your doctor may apply pressure to an artery in your neck. For some types of SVT, this can help stop your heart beating so rapidly.
• Valsalva manoeuvre. This involves lying down and blowing forcefully into a syringe, increasing the pressure in your chest. 
• Having antiarrhythmic medicines, such as adenosine or verapamil, through a drip into your bloodstream.
• Electrical cardioversion. This uses an electric shock to restore your rapid heartbeat to normal. 

Long-term management

Whether or not you need any long-term treatment depends on a number of factors. These include the type of SVT you have, how often you get symptoms, how long they last and how they affect you. 

Self-help

Your doctor may talk to you about certain things that can set off your SVT, and how you might be able to avoid them. These may include caffeine, alcohol, smoking and taking illegal drugs. If you can cut down or stop taking these, your SVT might reduce or stop. Certain medicines or other health conditions may also be linked to your SVT, and your doctor can help you to manage these. Your doctor may teach you how to do the Valsava manoeuvre yourself (where you blow out forcefully to stop an attack of SVT). 

Catheter ablation

You might be offered a procedure called catheter ablation, particularly if you keep having regular attacks of SVT. This procedure involves inserting a small tube called an electrode catheter into a vein in your groin and using X-rays to pass it up to your heart. Radiofrequency waves are then delivered via the catheter to destroy any tissue that's causing the abnormal electrical signals in your heart.

Medicines

You might be prescribed medicines to prevent further SVT episodes. These may include:

• beta blockers
• calcium channel blockers
• other antiarrhythmic medicines, such as amiodarone or flecainide

Always read the patient information leaflet that comes with your medicine and ask your pharmacist or doctor if you have any questions. 

Causes of supraventricular tachycardia

Supraventricular tachycardia (SVT) is usually due to extra pathways between the upper and lower chambers of your heart (the atria and ventricles). But most people with SVT are otherwise healthy, and don’t have any underlying problem with their heart or other health condition that causes SVT. Occasionally, other problems affecting your heart, such as a previous heart attack or surgery on your heart can lead to SVT.

If you get SVT, you may find that various things that can trigger it, such as: 

• certain types of medicine
• drinking a lot of alcohol
• caffeine
• smoking
• taking illegal drugs such as cocaine or speed