Try not to be scared...what is your heart surgery for?
I had 2 heart surgeries 3 years ago and yet here I am perfectly well. I even had a major complication that required more surgery to keep me alive yet I suffered no bad effects and am perfectly well today.
The doctors do not send you off to surgery just for fun or practice etc...they do it because it is needed to save your life.
Sounds like you need some suport or to talk with people who have already had this surgery and are now living a totallt normal life again. There are a lot of heart groups available and most likely one especially for people who have the same problem as you. I found a valve replacement
group a few months before my surgery and they helped me face my surgery with absolutley no fear. I was actually excited to get fixed.
I wish you all the best.