Just curious how were you diagnosed. I am seeing a neuro in a week. I have gastroparesis and feel "ill" most of the time. i had an abnormal tilt table test, but did not pass out. What has been your experience. i am 38, if you don't mind me asking how old are you?
I think it may be due to the fact that your heart is under the control of The autonomic nervous system.
This consists of two seperate and distinct little systems.The first, known as The sympathetic nervous system, works on the heart to speed it up. The other, the parasympethetic nervous system works to slow it down. When you're normal and resting, your parasympathetic is dominating control of your heart so your heart rate is usually around 72 beats per minute. When you're exercising or running around, the sympathetic nervous system takes over and you get an increase in heart rate.
What happens in autonomic failure is these two systems essentually get turned off. However the heart can beat on its because it has an inbuilt system that allows it to beat itself. The only problem is, the hearts only inbuilt beating system operates at something like 80-100 beats per minute. This may wxplain the increase in heart rate.
The decrease in blood pressure is to do with the sympathetic nervous system. This works (aswell as to speed up heart rate) to tighten the blood vessels to keep them tense. The blood is under pressure to get through these narrow vessels. The healthy bp measurement is 120/80. When your autonomic nervius system breaks down, the vessels are no longer under a tension grip, so they relax, so the blood is under less pressure because the vessels are wider. This should explain the drop in blood pressure but rise in heart rate.