Supraventricular Tachycardia

Recurrent episodes of rapid heart rate arising in the upper chambers of the heart

  • Most common in children and young adults
  • Sometimes runs in families
  • Exertion and consumption of alcohol and caffeine may trigger attacks
  • Gender is not a significant factor

Supraventricular tachycardia (SVT) is a type of arrhythmia caused by a fault in the electrical pathway that regulates the heart rate. During an episode of SVT, which may last up to several hours, the heartbeat is rapid but regular. The heart rate rises to 140–180 beats per minute and sometimes climbs even higher. In a heart that is working normally, each heartbeat is triggered by an electrical impulse from the sinoatrial node (the heart’s pacemaker), located in the right atrium (one of the heart’s upper chambers). The impulse passes to a second node, the atrioventricular node, which relays it to the ventricles. In SVT, the heartbeat is not controlled by the sinoatrial node. This problem may occur either because an abnormal pathway develops, causing an impulse to circulate continuously between the atrioventricular node and the ventricles, or because an extra area of cells develops and sends out pacemaking impulses.

SVT may first appear in childhood or adolescence, although it can occur at any age. In some cases, SVT is caused by an inherited abnormality in the heart’s electrical pathways. Episodes generally occur for no apparent reason, but they may be triggered by exertion and by caffeine and alcohol.

What are the symptoms?

The symptoms of SVT usually develop suddenly. They last from a few seconds to several hours and include:

  • Palpitations (awareness of an irregular, abnormally rapid, or heavy heartbeat).

  • Light-headedness.

  • Pain in the chest or neck.

In rare cases, a prolonged episode of SVT may reduce blood pressure to a life-threatening level.

Supraventricular tachycardia (SVT)

Impulses from the sinoatrial node normally control heart rate. One cause of SVT is an abnormal electrical pathway, which allows an impulse to circulate continuously in the heart, taking over from the sinoatrial node.

What might be done?

If your doctor suspects that you have SVT, you will probably have electrocardiography (see ECG) to record the electrical activity of your heart. This investigation may last 24 hours or more (see Ambulatory ECG) because SVT occurs only intermittently. You may have further tests to look for abnormalities in the heart’s electrical pathways (see Cardiac electrophysiological studies).

If your doctor suspects that you have SVT, you will probably have electrocardiography (see ECG) to record the electrical activity of your heart. This investigation may last 24 hours or more (see Ambulatory ECG) because SVT occurs only intermittently. You may have further tests to look for abnormalities in the heart’s electrical pathways (see Cardiac electrophysiological studies).

People who have occasional, brief episodes of SVT can control the symptoms by stimulating the vagus nerve, to slow the heart rate. One way to stimulate the nerve is to rub the area over the carotid artery in the neck, although this is not recommended in adults over the age of 50 because it may precipitate a stroke. Other techniques include plunging your face into ice-cold water or straining as if moving one’s bowels. Your doctor can teach you these techniques.

Troublesome episodes of SVT may be treated with long-term antiarrhythmic drugs. SVT may be cured by radiofrequency ablation, a treatment carried out during cardiac electrophysiological studies. This treatment destroys abnormal electrical pathways but carries a small risk of causing complete heart block, in which the heart’s electrical system fails. In most cases, SVT does not affect life expectancy.

Test and Treatment: Cardiac Electrophysiological Studies

From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.

The subjects, conditions and treatments covered in this encyclopaedia are for information only and may not be covered by your insurance product should you make a claim.

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