I went to the er myself a few weeks ago for the same thing. It ended up just being a panic attack because after they gave me ativan I started feeling better. Do you have any anti-anxiety meds? If so I would take that and just try to relax. If you were having a heart attack your left arm would be numb and would have trouble breathing. Hope you feel better soon.
That happened to be in the past too, when I was coming off of Klonopin. I went into a major episode with some symptoms of possible serotonin syndrome, so they gave me ativan and I got better. Whatever caused it, the chest pains/palpitations were actually similar.
I'm still feeling sick, and I am still having the weird heart beats. The chest pain has dulled now, and I only have some heart burn from throwy-up stuff.
Also, I only take Prozac right now...no axiety-only medications.