I can understand how you feel (I know, not exactly--each of us reacts differently). Anyway, I went through the same thing with my mother several years ago. Although, it is normal to be upset, worrying will not help. You will need your strength -- so you need your sleep.
So, find a way to relax (take a relaxing shower) and get some sleep--or at least lay down and close your eyes. If you have to cry--cry a little and let the tension release. Then think about all of the good times you have had with your Dad. These are gifts of life. Appreciate them. If you are a religious person--pray. Faith can be very helpful at times like these. If you have family to talk to, plan on calling them in the morning and make sure you have social support through all of this. Inform yourself about the procedure that he will go through. Maybe there is something else he needs for you to do for him. Things that he had to be interupted due to his heart attack
See what you can do to help him through it--emotionally. It might be just being there with him as much as you can. That is the best support. Make plans to do what you can for him or other family members that are involved. This can be a very healing time for you and him/them. Spending special moments together. Bypass surgery
can give a person a new lease on life. Men seem to respond much better as they have large blood vessels. You need to think positive and feel confident that he will come out of it okay. You need to convey and feeling of hope for your father so that he can pull through and heal.
You will be in my thoguhts and prayers. May peace be with you.