My dad has had a couple and had a double bypass a few years ago.

Although we aren't very close at all I think the majority of your concern may lie more in the fact that you are seeing the strongest man you know in your life starting to age and show signs of weakness. Just remember he is human too and more importantly no matter what may happen he is your father and needs your support.

This is where your relationship will change and instead of him being your strength you will become his.