Brett,
While one can look at this as an unfortunate situation, the bright side is that a bypass is possible.
When my mother had her series of heart attacks (which were painless -- we were treating her for pneumonia at the time) in 2001, by the time she had cardiology testing done, the damage to her heart was very severe. Additionally, 3 out of 4 of the major coronary arteries were completely blocked, and the last one was blocked in excess of 90%. The doctors called me aside before mom was even completely awake, and explained the whole thing to me. She didn't have a single healthy place to graft from. No bypass was possible. A heart transplant would have been the treatment of choice, but she was a diabetic, which automatically disqualifies you from the transplant candidacy.
They told me that a mere 5 years before that, this would have been a death sentence, but that advances in medication had come so far, that they could offer some hope of at least some improvement. So, that's the way it went.
2 years later, and she was the subject of a case-study for the drug "coreg", because her heart function, once below 15% (considered moribund) at the time of her hospitalization, had returned to the "normal" range of 85% (better than mine).
Mom is alive, and feeling better than she has in 10 years. They installed a defibulator/pacer, to act as a "watchdog", to prevent "sudden cardiac death", in the event she should develop a lethal arythmia, which has never had to function so far. It is better, though, to have the watchdog, and not need it, than to need it, and not have it.
Additionally, her heart, which had enlarged to 3X its normal size during the height of her disease, is approximately normal sized now.
Cardiology has come a long way in the last 10 years. What I found to be most important in Mom's recovery, however, was to be pro-active about things, ask all the questions you need to, and not be afraid to voice your concerns. Sometimes you do think of things that the doctors have overlooked, which can be important. If the doctor changes a medication, make sure you know the reason why, and make sure that he does as well.
I will note that mom did take a mild stroke this summer after her doctors decided to take her off of one of her blood thinners against my recommendations. They did apologize to me later, and thankfully, she recovered completely, but the apology would have been meaningless if she had not.
While it is not possible for you to become a cardiologist overnight, you can, however, become an expert on your father's particular condition, symptoms, and medications. Doing this will help him understand what is going on better, and be less afraid of his disease as well.
The human respiratory and circulatory system are much simpler to understand than the governor of a farmall cub.
I mean all of this, Brett, in the spirit of empowerment, and encouragement. With prayers, good wishes, and a little luck, your father will come through this just fine. But that, unfortunately is only half the battle of recovering from severe heart disease.
Namaste,
--Tom