I too have had pain in the chest when I suffer a panic attack but i get so weak and my legs and arms shake so bad, that I forget about the chest pain. Isn't that crazy? Anyways, I had all the tests you mentioned and they found nothing. I wore a holter monitor for 2 days and had to press a button everytime i had a panic attack during those 2 days, but it was inconclusive. They found nothing. I then had a stress test done, i ran on a treadmill all hooked up to monitors and then immediately after i ran, they laid me on a table and took an ultra sound. They did find something. I have mitral valve regurgitation. It is very common in people with mitral valve prolapse but the odd thing is, I do not have a prolapse valve which my doctor thought was very strange. Anyways, while I go through a panic attack, my heart races incredibly, like I ran a marathon, and then my mitral regurgitation kicks in on top of the panic attack.
My advise to you is to get a stress test done with the echo-cardiogram. It will at least ease your mind if you rule that out.