Postural Orthostatic Tachycardia Syndrome is a condition of dysautonomia more specifically orthostatic intolerance, in which a change from the supine position to an upright position causes an abnormally large increase in heart rate.
I just got back from my NL today, and they suspect that I have POTS in addition to Chiari, which is very common together.
I often get palpatations but not in relation to positional changes which I think is an indicator of POTS. My blood pressure also fluctuates wildly sometimes. For a very long time it was high(POTS I think causes low pressure upon standing with rapid heartbeat). Now my pressure is pretty stable except when I lie down...then it goes very low(80/50). Abby, let me know when your testing is and how it goes.