A rheumatologist is certainly the way you want to go if auto-immune is a likelihood. Just do some research ahead of time and be aware that it can take months to get in to see a good rheumatologist. I always want to remind folks that not every doctor graduated at or near the top of his or her class. There are marginal students in medical school, just as in any field.
My first rheumy was a jerk and felt that sarcasm was a good substitute for answers. When he put me on prednisone he told me to stay out of the sun. As I had commitments at that time that required me to be outdoors for 8-10 hours at a time, I asked him what would happen if I went out in the sun and his answer was for me to try it and find out. NOT the sort of medical advise I wanted or needed. Just one of many reasons he WAS my rheumatologist.
So do your research and if your doctor is giving you non-answers or is reluctant to order tests that you feel you need, or is just generally unresponsive to your needs and your questions, fire him and find another doctor. Your health is too important to put in the hands of someone who is just going through the motions.
I would definately try to see a rheumatologist.
They deal with auto-immune, and connective tissue disorders.
The best thing is to do a little bit of research, to sift out the good ones from the bad,
Cant the cardiologist refer you on to one, seeing as he mentioned one of the tests suggesting auto-immune, maybe then you will get seen a lot quicker.
Good luck
Nicola