I know this may not be relevant, but since it is my experience with the symptoms you describe above, I'll put it out there for your consideration. Initially my symptoms were ascribed to anxiety, too. And I have a family history of irregular heartbeat, so it was also suspected this played a role. When all the dust settled, and I insisted on having a sleep study because I knew I snored, I was diagnosed with severe sleep apnea and began cpap therapy. After that my irregular heartbeat and tight chest improved tremendously. (The tight chest was caused by straining to breathe.) I still have some irregular beats now and then, but not like before. I can't remember now if it was 1300 or 13,000 PVCs in 24 hours, but for awhile there I didn't have normal beats. Now irregular beats are rare and happen mostly when I'm sick or really tired. I hope you find some relief soon.
I have Lyme; it doesn't have me.