Dobutamin Stress Test

I'm not sure if anyone can help or not but I thought I would give it a shot. I am writing in regards to my mother. She is a 59 year old woman wilt pulmonary hypertension. She recently went to see a cardiologist and that doctor recommended that she have an echo and a dobutamin stress test. My mother is really strugling with wether or not to have the stress test done. My mother is an rn, she is about 4 foot 9, she has very bad scolios and very bad asthma. She gets short of breath just walking from her car parking lot to the hospital where she works. My mother is dealthy afraid of having this done, she is scared that the medicine will cause her heart to beat faster than she can breathe and her heart will just stop. She has expressed these concerns to the doctor and his response was that he does these tests all the time, but my mother knows probably on patients with bodies like hers. She's basically a 59 year old woman in a an 8 year olds body. She was supposed to have it done on friday and has decided to postpone it. I just thought I would post something on here and see what I get back. Any help would be greatly appreciated.
Thank you