I have no idea why this happens and I am guessing it has something to do with the RSD and with stress. It always happens when I am under a lot of pressure, a lot of stress or when I am very nervous for some reason. I do know that I don't handle stress the way I used to. I was extremely pressure-resistant until RSD hit. I lived off of stress before!

Maybe it's due to the nervous system reacting the wrong way, maybe it's part of it?

I do know that I don't have heart problems. I went to a cardiologist many years ago for a full check-up and he didn't find anything except that my heart reacted as if I were very out of shape; but no wonder - I could barely move due to the RSD. One test couldn't be completed, I remember, because I had to ride a bike for it and that was no longer possible by then.