Supraventricular Tachycardia

What is Supraventricular Tachycardia?

Often abbreviated to 'SVT', this condition is where the heart develops an abnormally fast heartbeat ('tachycardia' means 'swift heartbeat').

It is caused by a malfunction of a component of the heart located in its upper section ('supraventricular' section) called the SA node or 'sinus node' which controls the heartbeat via electrical impulses.

It is not uncommon for the heart to beat at 150 or even over 200 beats per minute during an episode of SVT.  Episodes generally do not last long, normally no more than 15 minutes, although in rare cases they can last a lot longer.

Supraventricular Tacchycardia is split into different types including  AVNRT, AVRT and Atrial Tachycardia (see also Atrial Fibrillation). The exact type is determined by testing (see below).

What causes SVT?

Medical science does not fully understand what causes SVT, however the condition is known to be triggered by anxiety, exercise or other sudden physical movements, caffeine and alcohol and usually involves a short circuit of the electrical pathways in the heart.

What are the symptoms of SVT?

The following are common symptoms of SVT...

  • Rapid heartbeat/breathing
  • Chest pain
  • Dizziness
  • Shortness of breath
  • Sweating
  • Anxiety

In rare cases sufferers may faint and it is common to feel very tired after an episode of SVT. In very young children it may be difficult to spot these symptoms, although lethargy, shallow breathing and a lack of interest in food may indicate the condition.

See also advice on symptoms of a heart attack here.

How is SVT diagnosed?

The most common way of diagnosing SVT is with an ECG (electrocardiogram) to measure the electrical impulses of your heart. Other ways of checking an irregular/fast heartbeat include...

Is SVT serious?

Most cases of SVT are benign, ie not serious and with no serious effects on the heart or the body.

How is SVT treated?

If episodes are very rare, treatment may not be necessary. Sometimes coughing or pressing down (as if you are having a bowel motion) can slow the heartbeat down. Where SVT is continual, the following treatment options are available...

  • Special medication to control the heartbeat rhythm
  • Cardioversion - the application of a mild electric current to the heart
  • Ablation - a treatment using either heat (radiofrequency ablation) or cold (cryoablation) on the section of the heart sending the abnormal electrical impulses