Does everyone have "clogged" arteries but do well with them?

My BFF’s s/o developed a blood clot in the area of his brain that controls vision . His vision is alright a couple days later but what concerns us is they are going to check out the arterial system around his heart to see if he needs a bypass. What are the chances, knowing these are heart surgeons, of them saying his arteries are fine and dismissing him? He is 75 with no chest pain. I’m hoping the worst that will happen is he’ll have a Cath.