Can you fail the cardiac stress test due to shortness of breath caused by obesity ......

I had to do the IV test due to my right knee being messed up. I had zero problems with it. The anticipation was worse than the actual test. 

Good luck. 

The cardiac stress test is no big deal.  I don't know your age, but I am in my sixties.  I had the chemical stress test done a week before surgery and did fine.  My knees, at that time, hurt too much to walk quickly on the treadmill.  I can say this now because I am six months out, but don't stress yourself out.  Your doctor ordered this test because he thought it was necessary.  Please calm down and stop stressing out.  I know, again this is easy for me to say because all of this is behind me.  I didn't even have time to stress out over the upcoming surgery because my stress test results came back the very same day as my last visit to my weight loss surgeon for pre op.  I actually had to drive to the doctor's office who said they never got the paperwork for the pcp to sign off on the surgery, I know they did.  My weight loss surgeon faxed it that day 3 times.  I was so tired after my trip to the pcp and the weight loss doctor that I slept for an entire day.

I wish you the best.  I suffer from severe anxiety and take antidepressants and the chemical stress test did NOT make me feel sick. 

The goal of the stress test is just to get your heart rate above a certain level for a while, if anything, SOB will accelerate that. Passing ti isn't about your ability to get your HR up, but what your heart does while your HR is elevated.

Amusingly (for me anyway), I had to have a stress test a few months ago to evaluate some irregular beats I was having. They ramped my speed up fairly quickly, and I was mostly doing fine, and then I had to abruptly stop, I literally hopped off the treadmill. When my doctor e-mailed me about my results, he said he was surprised that I could only go for 7 minutes. I told him I could have gone much longer, but I was basically jogging at that point, with a full bladder, and having had two 8.5 lb babies. I could have kept going, but they would have had to santize the treadmill afterwards.

I've had the nuclear stress test because I have a bad knee. They take a scan of your heart first then inject your IV,  I didn't feel my heart racing when they injected the medicine it was more of a warm feeling then a little bit of pressure more than anything, it was really quick, after that they take an ekg then do another scan, and then you are given a caffeinated drink when it's done, I worried myself sick the prior week but it wasn't all bad than I expected, good luck!