Your thoughts will always trigger a panic attack. On the flip side, your thoughts can keep you from having a panic attack and can calm you when you are having one. Remember that just because you are thinking something, it doesn't make it a fact.
I also have a heart phobia. I find the more I think about it, the more I am aware of every little disruption in the beating. The more I am aware of every little disruption, the more I panic, and around and around the cycle goes. I've been dealing with this for about 12 years now and I am now learning through the Panic Program offered here that it's not my heart that's the problem. It's my thoughts. The program is free - take advantage of it if you haven't started already.
Go to your doctor and make sure there is nothing to be worried about with your heart. It's extremely common for panic sufferers to have fears about their hearts and to feel like their having heart attacks. If you browse through the messages, you will see how common this is. If your doctor tells you there is nothing wrong, then trust that there is nothing wrong. I know that's hard to believe when your heart is pounding out of your chest but remember when you are feeling this way that feelings do not change fact. I have to remind myself of this all the time, but it does help.
Hang in there! You are stronger than you feel - I promise!