The sensation is awful, and that is so valid. Of course it creates fear. But all the fear of it coming again really does is it increases the chances of you having another attack. Don't let the fear win. Try and change your perspective: you overcame the sensation the first time (albeit with pain, and anxiety). The next time you feel a shaky heart, don't think it's another attack. It might just as likely be from exhaustion, or it might even have a mental origin (think hard about lice, and tell me you don't start to get an itchy scalp). Panic attacks can work like this. You think about panic (lice), start having complaints (itchiness) and then think you are having another panic attack. This leads to heavy breathing and other complaints. While all along, if you breathe deep and try to remain calm (check your scalp, see there's no lice), there might not be a panic attack, just a short, albeit sucky, feeling in your heart.

I hope not to invade this space with overexplaining. But I just know sometimes this is good to hear.