I Have Had Past Problems With My Heart. They Originally

I have had past problems with my heart. They originally thought is was SVT but upon further examination they ruled that out. I have a rapid heart beat sometimes. It feels like it is going to pound out of my chest. Also something new has been happening. I get this odd feeling in my chest. I feel like my heart skips beats, and while it does this, my chest just feels empty and weird inside. I just want to know what that is.