I agree with Jack. ...Ask about stents and or being treated medically. Ask about all your options. he is 86 years old so let him live the rest of his life enjoying what he likes to do....with minimally invasiveness. Good Luck To You All.
Just from the information you supplied, you may have more options in addition to traditional bypass surgery (CABG). This is very traumatic surgery, especially for a person of 86 years.
Doctors will stent any blockages >70%. That is there rule of thumb. If this be the case the 2 80% blockages could be stented. The blockage at the top of the Lad may also have to be stented or maybe Rotational Arthectomy could be used. This can be a very dangerous procedure. I had it once. This can be used to clear arteries, but is not a popular procedure among cardiologist, I do not believe, due to the risk.
There is also a minimally invasive bypass surgery that can be performed on the Lad, and most times only the lad. This is much less of a traumatic surgery, but is not done in many hospitals.
Another big problem could be the general condition of all of his coronary arteries. As we age the inside of the arteries become calcified, diseased and sclerotic. Being just a layman with CAD, I could only guess that these arteries could be very hard to work with.
My Mother had 6X CABG at the age of 73. She did fantastic! She could not believe all of the energy she had. Before the surgery, the cardiologist that did the cath, told the children that he did not know how she was living. He estimated that she had 5% of the total amount of blood flow going to her heart muscle.
She died less than a year later of a hospital borne staff infection after minor surgery.
I believe that traditional bypass CABG would be extremely difficult on you FIL. I guess I would listen to the doctors, but do ask about stents, Rotational Arthectomy, and minimally invasive bypass surgery, or MID-CAB.
Best,
Jack