Why sign this? What's to say that there won't be something in the (even near) future that will fix this? I know how you are feeling.. I do. I've had DNR orders for myself... (pre accident) ... I don't have any now... as things did change.

What you might want are forms expressing your wishes should you have to go on life support. You can fine tune your wishes... and make them very explicit.. (i.e. if you are on life support for xx days/weeks and 3 MDs have stated there will not be any change... then... ) I would even make sure they didn't just starve you to death...

If you fear your heart will not last anyway, a DNR isn't necessary, as they can't revive you if it fails... DNR means they don't try... If you don't have hope for yourself, then allow the medical teams have hope for you, and at least try. We don't know what's around the corner for us...