Health

Postural orthostatic tachycardia syndrome

CHECK-UP: My sister has been having fainting and dizzy spells and a fast heart rate

MARION KERR
Tue Mar 23 2010 - 00:00

CHECK-UP: My sister has been having fainting and dizzy spells and a fast heart rate. These symptoms usually come on after exercising but also when she stands up from a lying down position. However, lying back down seems to resolve the symptoms. What could this be?

It could be a condition called postural orthostatic tachycardia syndrome (Pots). Pots is a disorder where orthostatic intolerance (OI) is the main symptom. Orthostatic intolerance is when a significantly reduced volume of blood returns to the heart after a person stands up from a lying-down position. Symptoms of OI include lightheadedness or fainting. In Pots, these symptoms are accompanied by a rapid increase in the heartbeat (tachycardia) without a drop in blood pressure. Faintness or lightheadedness associated with Pots is usually relieved by lying down again.

Sufferers may be overwhelmingly fatigued after a bout, while sleep problems and migraine headaches have also been reported. The exact cause of the reduced return of blood to the heart that occurs in OI is not known, nor is it known why the heart beats so rapidly in Pots. It is thought they may be due to abnormalities in the sympathetic nervous system – responsible for decreasing muscle tone and increasing heartbeat in reaction to stress – or the parasympathetic nervous system, which does the opposite, or a combination of both.

My sister is in her 20s. Is this the usual age group affected by it?

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Approximately 80 per cent of those affected by Pots are women aged between 15 and 50 years of age. Pots can develop after a pregnancy, major surgery, trauma or a viral illness. Some women with the condition notice increased incidences of Pots just before their period. Exercise and heat can worsen symptoms and may result in individuals being unable to exercise because of the dizziness.

Can it be treated?

A special test known as a tilt table test is usually needed to confirm the diagnosis of Pots.

Many sufferers – approximately 90 per cent – will respond to medications and simple interventions such as adding extra salt to the diet, increasing fluid intake. They may also find some exercise programmes helpful.