Not only would a GAC not be a help to you (that I can see,) there will be rides WDW does not recommend for people with high blood pressure--basically anything fast or jerky has warnings against riding. You probably need to also check the ride descriptions in the FAQs at the top of this thread to see what rides would best be avoided.
With that said, there is a lot that you can do. A lot of research, fastpasses and a good touring plan are your friends!! The more you know, the better time you will have. A GAC will not speed up your ride access and will often make it actually take more time. I'm speaking from experience on these issues.