I must admit, during my first panic attack I was convinced I was having a heart attack, grabbed the phone and prepared to dial 911. Then I was put on meds and the panic attacks went away.
After the birth of my daughter they came back. I know logically that I'm not having a heart attack. I've gone to the doctor, been tested for just about every heart problem just to be on the safe side, got a full physical, and discovered that physically I am 100% fine. I don't even have any risk factors for heart problems except for being overweight.
Now when I have a panic attack I can logically tell myself, "I'm not having a heat attack. I'm not having a heat attack." Nevertheless, everytime I have one there's that little voice that says "What if? What if you are having a heart attack? What if the doctor missed something? What if you're going to die right here right now?" It has been very difficult to control these thoughts, but I'm getting better at it.
The most helpful thing I've learned is that chest pain usually gets better when you get up and move around when you're having a panic attack. If you're having a heart attack it gets much worse. So, when I start to have chest pains I make myself walk around the house, the yard, the neighborhood, etc. If the pain gets better, I can put my mind to rest.