I believe I have the same thing.
I wish Iknow though whether it's the panic attacks that have started my tachycardia or the other way around.
It seems to be like a vicious circle and no doctor can give me a straightforward answer.
I've been to the ER too many times, I've had a whole bunch of tests all of which showed doctors no reasons to believe thare is something wrong with my heart, still I have these weird chest pains, it's like my upper ribs are on fire, and they radiate to my back, my arms ... it's a mess. I've been told to take ibuprofen as it looks like it's costochondritis and it will go away in 2 weeks...
I try to think positively, I try to reasuure myself that it will go away, but then the pain comes back and I'm back to square 1.
It's somewhat comforting to know there are these forums where people share their stories, but there are so many of us who have these problems, yet there is no black and white answer/solution.