Supraventricular tachycardia - Causes of supraventricular tachycardia (SVT)

Episodes of supraventricular tachycardia (SVT) occur because of a problem with electrical impulses in the heart.

Heartbeats are normally initiated by a small group of cells located in the top of the heart called the sinoatrial node, which acts as the heart's natural pacemaker. The sinoatrial node produces electrical signals that are sent through muscles of the upper heart chambers (atria), causing them to contract and pump blood into the lower heart chambers (ventricles).

The signal then passes into another group of cells located in the middle of the heart called the atrioventricular (AV) node. From here, the signals travel into the ventricle muscles, causing them to contract and pump blood out of the heart.

Episodes of supraventricular tachycardia occur when a problem develops in this system. This causes faster signals to be sent around the heart, increasing the speed at which the heart beats.

In most cases the problem is temporary, lasting for a few seconds, minutes or hours.

Types of supraventricular tachycardia

There are several different types of SVT, which are classified by the specific problem in the heart that disrupts the electrical system.

A type of SVT called Wolff-Parkinson-White syndrome occurs due to an abnormal electrical connection between the atria and ventricles, which creates a short circuit in the heart's electrical system. This happens because people with Wolff-Parkinson-White syndrome are born with a strand of extra muscle tissue between these chambers.

In other cases, a short circuit occurs even though the heart is otherwise normal and some cases are caused by an electrical signal from another part of the heart overriding the signal from the sinoatrial node.

Supraventricular tachycardia triggers

SVT is usually triggered by extra heartbeats (ectopic beats), which occur in all of us but may also be triggered by:

some medications, including asthma medications, herbal supplements and cold remedies
drinking large amounts of caffeine or alcohol
tiredness, stress or emotional upset
smoking lots of cigarettes