My brother took the treadmill stress test and he is a conditioned athlete but said the same thing "the most uncomfortable experience ever". He had bad chest pains (the presenting reason for the test) but the test was completely normal. His turned out to be due to a muscle problem in his chest. I have to get one in a month and I am scared witless, even the feeling of tachycardia is enough to give me a panic attack. Good luck.
My last Thallium stress test was chemically induced due to a ruptured MCL. I can tell you I had the same sensations, sudden SOB, rapid heart rate and a tight chest. It started the instance they started the drip and it stopped within a second or two of stopping the drip. It was one of the most uncomfortable experiences of my life. The results were totally normal and exactly the same as the previous year, I had expected bad news as well.
Go figure........
Jon