"Often more simply referred to as postural tachycardia syndrome, or POTS, this disorder is characterized by the body's inability to make the necessary adjustments to counteract gravity when standing up. The defining symptom of POTS is an excessive heart rate increment upon standing. However, as you will discover, there are a multitude of other symptoms that often accompany this syndrome. As such, POTS can be a difficult disorder to detect and understand. Our web site provides an overview of POTS and contains sections on symptoms, mechanisms, causes, tests, myths, links and research. There are also sections with information on what may help or hinder POTS patients." http://dinet.org/
I have not been tested for POTS - however I do have strange heart and blood pressure issues. It is common in Chiari and EDS patients.