what is OI?

My question is what is OI and what does it stand for. I'm not talking about Osteogenesis Imperfecta, I'm talking about the heart condition where most people are diagnosed after having a tilt table test. I know that the I stands for Intolerence, but thats it. Please answer my question i need to know all i can about the condition/disease.

[kenkeith]

Orthostatic intolerance (OI) is the development of symptoms while standing or sitting upright.  It has been associated with chronic fatigue and immune dysfunction syndrome (CFIDS) in both adults and children.
Unlike those with OH (orthostatic hypotension), which occurs within the first three minutes of standing, meaning that heart rate and blood pressure changes don't develop for many minutes after standing (OH), making the standard in-office test for acute orthostatic hypotension ineffective in diagnosis...dx with tilt table.

[Tom111764]

I get light headed, and dizzy. I also get, what I have been told is Visual Migranes (migraines) where I can see fine but I have prizm like diamond around my vision.  I can be perfectly fine on e minute and the next minute I get a rush of panic and I black out and actually pass out most of the time. When I come to, I am sweating really bad and at time I have to vomit.  Also when I have to cough really hard I start blacking out and have to take deep breathes to recover. Has anyone exprienced this?

[Mom2four85]

Here is some info and links for Dysautonomia or Autonomic Dysfunction - http://www.medhelp.org/health_pages/Neurological-Disorders/Autonomic-Dysfunction--Dysautonomia-Index-Page/show/857?cid=196

You should ask for a tilt table test if you haven't had one done to see if they can find the cause of your blacking out.  If you click on the FAQ link there is a list of questions and symptoms that may be familiar as well as links for doctors around the world.