A form of dysautonomia.  Often abbreviated as POTS, it is an abnormal increase in heart rate upon standing.   POTS is diagnosed by a tilt table test, or prolonged standing test, and a test is considered positive for POTS when an adult experience an increase in heart rate of 30 beats per minute within ten minutes of standing (or 40 bpm for an adolescent), or if the heart rate reaches 120 or above.  A diagnosis also requires that a patient experiences symptoms such as lightheadedness, syncope (fainting), shakiness, fatigue, anxiety, nausea, vomiting, sweating and fatigue.

Triggers cause a sudden drop in your heart rate and blood pressure.  This sudden drop reduces the amount of blood flow to the brain, which in turns causes a loss of consciousness. This form of syncope (fainting) is most commonly triggered by things such as; the sight of blood or extreme emotional distress.

However, there is a form that requires no trigger. Instead the drop in heart and blood rate comes from a miscommunication between the brain and the heart.  When you stand, blood naturally pools in your legs and it requires a signal from the brain to the heart with adrenaline in order to redistribute the blood back to the top half of your body.  With this type of syncope the signal gets misinterpreted and instead of adrenaline, the heart is told to slow down even more.

An episode should resolve itself rather quickly, usually less than a minute.  However, you run the risks of fainting again if you stand too quickly after an episode.  The greatest risk comes from falling and hitting your head.

Symptoms; pale skin, lightheadedness, tunnel or blurred vision, nausea, warm sensation, clammy sweat,