I sorta know what you're worried about. My dad has suffered 2 major head injuries (1 technically fatal), and has had 2 strokes.
When he had one head injury, he stroked on the operating table, and his heart fully stopped for a time, and just pulled through, then when recovering, he stroked again and his heart suffered quite a bit of damage then.
He keeps going though, and he sits at the base station when I'm snowboarding, and he'll go sledding and dog-sledding with me easily enough.
From my experience, is if he was in good health before hand, with a strong heart, he should be OK.
I also have a mate who's dad was stabbed straight through the heart with a screwdriver (for a frickin leather bag
) and he's fine.
With any medical condition, it all depends on the individual. I hope that your dad doesn't have another one, but at least they were a while apart.