Any form of deconditioning of muscles can lead to higher blood pressure, which includes MG. The heart is not the only thing which can effect high blood pressure.

There is "essential" and "secondary" hypertension. It is very important that a cause for the high BP be thoroughly investigated before a blood pressure drug is thrown at you. Many times the cause can be improved or eliminated (such as a drug). And going off of a hypertension drug can actually cause a spike in BP, greater than it was before the drug.

http://www.aafp.org/afp/2003/0101/p67.html
http://enotes.tripod.com/hypertension2.htm
http://www.nejm.org/doi/pdf/10.1056/NEJM198004033021402

Higher BP should ALWAYS be investigated. My Dad had high BP, which was not diagnosed by his doctors, due to aortic insufficiency (due to rheumatic fever) and this caused his kidneys to fail.

Renal artery stenosis is one of the main causes of secondary hypertension. This can be determined by a duplex ultrasound (easy test, I've had it done).

I hope they can figure this out, Debra.