How long in hospital after a heart attack?

My dad just had a massive heart attack 6 days ago. It was as bad as it gets and they told us the whole time that he was probably going to die. It's a miracle that he survived! And now he's been awake for almost 4 days. His short term memory was initially very, very bad and he would forget things minutes after you told him. We see small improvements now, but we are told it will likely take at least a few months to get better, but there is no guarantee that it will come back completely. I am having a hard time finding much solid information about this on the internet, and every nurse I talk to seems to have a little different idea about if he's showing enough improvement for us to feel that he will recover his short term memory loss completely. From what I understand, it is a case by case situation... some people will recover their short term memory, some not at all, and some anywhere in between.