Whether he was aware of that was not clear. There are a lot of instances where people have heart attacks and are not aware of them, especially when your jobs require you to do things that require you to get hurt.
To see this kind of heart disease in someone this age is not common, but it usually means there are certain risk factors that allow the plaque to build up in the arteries much earlier than in some others. Heredity can play a large role in that.