A tilt table test is used to evaluate the cause of unexplained fainting or severe lightheadedness.
During the test, your blood pressure and heart rate are monitored. You begin by lying flat on a table. Then, the table is tilted to raise the upper part of your body — simulating a change in position from lying down to standing up. This test allows doctors to evaluate your body's cardiovascular response to this change in position.
When you stand up, gravity causes blood to pool in your leg veins, reducing the amount of blood that returns to your heart. This causes your blood pressure to drop (orthostatic hypotension). Normally, your autonomic nervous system rapidly accommodates this effect by narrowing (constricting) your blood vessels and increasing your heart rate. But if these mechanisms don't work normally, the drop in blood pressure can be severe enough to cause fainting.
The tilt table test can help detect orthostatic hypotension. Causes of orthostatic hypotension may include diseases that affect the autonomic nervous system, such as diabetic autonomic neuropathy and Shy-Drager syndrome.