Why would I need a tilt table test?

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There are several reasons that you might be prone to lightheadedness or fainting, and your doctor needs to know the reason before deciding on the right treatment. The tilt table test helps to diagnose the most common cause of fainting, a condition known as neurocardiogenic syncope. This form of syncope goes by several other names, including neurally mediated syncope and vasovagal syncope.

Neurocardiogenic syncope is caused by problems in the signals sent by the brain and nervous system to the heart and blood vessels. Typically, your body overreacts to some trigger, such as a frightening situation or the sight of blood, but some people faint after simply standing up for a long time.

Here is what happens: Imagine that you are about to give a speech and you are really nervous about it. One part of your nervous system (the sympathetic nervous system) reacts to your emotional distress by causing the heart to beat faster and the blood vessels to constrict, both of which cause the blood pressure to go up. This feeling of “butterflies” is completely normal and nothing to worry about. Your body has a back-up system, the parasympathetic nervous system, which keeps the blood pressure and heart rate from getting too high.

Usually the two systems work together very smoothly. However, if you have neurocardiogenic syncope, the parasympathetic nervous system eventually overreacts, causing the heart rate to suddenly slow down and the blood vessels to relax. As a result, your blood pressure falls abruptly, the blood pools in your legs, your brain is deprived of blood flow, and you become dizzy or faint. When that happens, the parasympathetic nervous system backs off, and you regain consciousness.

The tilt table test attempts to trigger the parasympathetic nervous system to overreact by tilting you from lying flat to nearly upright. This change in position causes the heart to beat harder and faster and the blood pressure to rise, just as happens during emotional distress or a sudden fright. Most people who have neurocardiogenic syncope will become lightheaded or faint during a tilt table test, although it may take 30 minutes or more before the parasympathetic nervous system goes into overdrive.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.