SVT, or Supraventricular tachycardia, is a condition which causes your heart to beat too fast – this generally means a rate of around 130 to 250 beats per minute. This arrhythmia is caused by damaged electrical signals in the heart, and often affects young healthy people. The episodes of quickening heart pace are usually temporary and disappear without the need for treatment. The length of these episodes varies, from a few seconds to a few hours, depending on the individual. Our heartbeats are controlled by electrical impulses which begin in the muscular wall of the heart, known as the sinus node, and travel through the heart to make it contract. These signals travel from the atria, the name for the upper chambers of the heart, to the ventricles – the lower chambers. When there is an extra electrical pathway in the heart, this leads to SVT – the signals result in a short-circuit, which means they end up travelling around the heart in a circle. These types of SVT are known as re-entrant tachycardias, or paroxysmal SVT, and their symptoms are temporary but very sudden.
There are three forms of SVT, which have varying symptoms. The first is called atrioventricular nodal re-entrant tachycardia, or AVNRT, and occurs when there is an extra pathway situated in the AV node. The second is referred to as atrioventricular re-entrant tachycardia, or AVRT, and occurs when the extra pathway connects to the atria and ventricles separately through the AV node. Lastly, atrial tachycardia is a less common form of SVT but arises from the atrial tissue in an area other than your sinus node. SVT is characterised by palpitations, shortness of breath, chest pains, or dizziness and fainting – the latter of these symptoms is very rare. It is important to remember that such symptoms may be associated with other health problems, though, so a check-up with your GP is advised if you think you may have this condition. While this problem generally sorts itself out, that isn’t to say it is without its set of complications. For example, if you have SVT, your heart may not be able to pump blood as effectively around your body – this can result in low blood pressure. Low blood pressure is not only attributed to fainting, but also to less blood flowing to your heart (known as ischaemia). This can lead to heart failure if particularly severe, though these problems are more common if you have other problems with your heart.
While researchers are unsure why some people develop SVT, there are certain factors which are known to be related to the problem. These include specific medicines, previous problems with your heart since birth, hormonal changes, alcohol, caffeine, emotional or physical stress, smoking, or taking illegal drugs such as ecstasy or cocaine. You should seek medical advice if you think that you have this problem, so that your GP can examine you and check for any signs of the condition. If they suspect that you may do, they will run blood tests, take an echocardiogram, or perhaps do an electrophysiological study – this uses electrode catheters which stimulate your heart so that your GP can examine the electrical activity in closer detail. Depending on the risks to your health, they may do more in-depth studies to examine the activity within your heart. SVT is easily treated and there are various options for treatment, but these will depend on the severity of your problem – your doctor will be able to advise you of the options available to you.
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