I went through a very similiar situation with my father 12 years ago, but we found out about it because he had a stroke. He was 100% blocked on the right hand side and 95% blocked on the left hand side. Like your father, his arteries in the back are also blocked at about 80%. I remember the surgeon said that the arteries in the back of the neck carry a 20% mortality rate in order for them to be repaired. They put him on medication to control the situation. He was doing great until about 5 years when he suffered another stroke. Same thing only they changed up his meds.
My father has horrible cholestrol, high BP, doesn't eat right, drinks, and still smokes. My father is only 64 and he has already had 2 strokes. The fact that my father doesn't take care of himself upset me, but it has been 12 years and unfortunately I can't let it ruin my life.
I am assuming they are going to control your dad's situation with medications. I know my father takes Aggrenox and hasn't had any problems since they put him on that 5 years ago. I wish you lots luck with your dad. Please harp on him for the smoking, we didn't really get after my dad at first and now it is too late. He hides when he smokes, it is like he is a teenager.
Shell
Why can't a cardiac doctor (intervential cardiologist) do angioplasty to clear the half blocked arteries and possibly clear the totally blocked artery. That doesn't require surgery, but your post doesn't indicate a reason why your father is a high risk for surgery?