It all depends on whether it's "stable" angina or "unstable" -the latter coming on randomly and unable to be controlled by regular medication. Stable angina
can be treated fairly easily and living with it is a bore, but bearable.
If it's the latter, (unstable), life becomes pretty unbearable, and quite literally, your survival is just a lottery, because it's simply a question of when you (inevitably) get your first (and subsequent) heart attack(s). If it's in a field, miles from anywhere, then that's where you'll probably be found later. If it's near Casualty /ER then you have a great chance of surviving.
But really, if you have it bad, why suffer, when as the previous Answerer says, a relatively simple operation will cure you and give you a new life? It isn't worth the pain and hassle trying to deal with it.
Mine was unstable, and in my day (1992) the op. was painful, bloody, and somewhat dangerous. Now the risks are minimal, techniques vastly improved, and you are up and about in days, not weeks.
Good wishes and good luck.