Heart catheter surgery for Atrial Septal Defect?

I am getting ready to have heart cath surgery for ASD, and I have heard from one or two friends that after the procedure, you are required to lie flat on your back for a full 24 hours, without even lifting your head. I am wondering if that is entirely true, and if it differs from procedures, since they're all different. My doctor gave me a booklet to take home informing me on the procedure and what to expect. I will be in the hospital overnight after the surgery. It says that after the procedure I should be able to sit up and even walk about. So this gives the impression that, no, I will not have to lie flat on my back for 24 hours, but that I can sit up, get up, and even walk around after. What is your experience? Thanks and God bless.