Chances of survival after a cardiac arrest?

My grandad suffered a heart attack 3 days ago, but he thought the chest pain was from acidity or heartburn so he didn't say anything. They finally took him to the hospital and now he is in the intensive care unit. He also happens to suffer from diabetes. And now they reported that his kidneys aren't functioning normally. He is conscious but I'm really scared. What are the chances of survival after something like this happens.