[Oneirophobia]

If he is just finding this information out (given that the report is dated for today), I would not be to hard on yourself that your dad/parents did not tell you yet.
Finding out those types of things can be hard, specially for parents or loved ones knowing they have family, it can take time to process themselves before telling others.
Give him some time to tell you, if he doesn't on his own, Its your dad, talk to him by the sound of it your close, and when he is ready I am sure he will tell you. If your not ready for that and maybe you want to try talking to your other parent, could help get some emotions out.
Sometimes its needed time for processing, and that's okay.
Heart issues can be serious, but can be lived with. Don't get worked up before talking to one of your parents, it might not be something he cant live with.
I hope this helps.
-Christine