ER claim denied as 'not medically necessary' - chest pains at 2am, what was I supposed to do?

I went to the ER in January because I woke up with severe chest pains radiating down my left arm. I'm 34, no history of heart problems, but I was terrified. Turns out it was a severe panic attack, which I've never had before. Spent 4 hours there, got an EKG, bloodwork, the works. Total bill: $6,400.

My insurance denied the claim. Their reason: "The condition treated was not a medical emergency and an emergency room visit was not medically necessary." They're saying I should have gone to urgent care instead.

I filed an appeal two months ago. They rejected it. I filed a second appeal - rejected again. Now they're saying my only option is an independent external review. I'm doing that but honestly i'm exhausted and starting to wonder if it's even worth fighting. Has anyone won an external review for something like this?