Bones,
Your concerns about symptomology differences, as well as your concerns about GERD differential diagnoses if you ever go to the ER,
are valid subjects for your docs to discuss with you. Have they talked about doing further testing, and if not, their rationale for their decisions?
It's hard to have any kind of abnormal test, much less anything cardiac. I had hyperthyroidism before I went hypo, and I had lots of irregular heartbeats and dizziness. It was attributed to my thyroid, but it was still very worrisome while it was going on.
The other valid concerns are about where the blockage is and what that means. If they haven't explained these things to you, let them know that any further info to help mitigate your concerns would be appreciated.
You've probably done these things, I just wanted to say I think wanting to discuss your concerns with your docs is more than reasonable, and is your right as a patient.
cats paw