Bless your heart, and Katie's too.
Years ago, I had a poodle with a heart murmer that was diagnosed when he was about 1 year old and he lived a full 12 years and died of completely unrelated causes. So please try not to worry. I know every little baby is different, but that goes to show you that it may not be as bad as you are thinking, even if you DONT find out any answers just yet.