During the test you will have your cardiologist present. (I wouldn't take a test unless mine is there, although I have heard of places where there was only a technician.) Your blood pressure will be monitored constantly along with your heartbeat. Sometimes you can even see it on the screen, depending on where the screen is placed. I prefer being able to see mine.
Most of the tests start with very slow treadmill. I would refuse the ones where they start really fast, and I ask before they start for the slow start because I don't warm up easily. I have once had the fast test, mainly, I think, because that doctor (not my regular doc) didn't want to hang around for a good test. I felt like hell after the short one, but was angry that the doc left and I felt like I was going to die. I quit that group because of being assigned to different docs each visit and not wanting to see that one ever again.
Try your best to keep going! It's hard, but getting to the point where your rate is where they want it will give better results.