Sorry, Debra, I didn't see your post right away. My back is killing me right now and I can't sit for long.
I can't remember, what drugs are you on? Always look to a drug as a culprit. It may or may not be your heart. Do you have much sodium in your diet? Sodium can raise the BP a lot! I hope they'll check your electrolytes too.
It may or may not be MG-related. My BP goes up a bit in between Mestinon doses.
You are off of Mestinon? Why? When MG is worse, it can raise both BP and pulse. Do you know what your O2 saturation is?
This may not be an issue but some people do have problems with IVIG. A person I knew had it "reveal" antiphospholipid antibody syndrome," which is common in people with autoimmune diseases.
I hope you will keep a journal of symptoms. And I hope you'll be ok. I know how scary it is to have a high BP and tachycardia. Let us know how things go!

Annie