"If I knew I was going to live this long, I'd have taken better care of myself."
Well Mickey - you can say that again..... and again and again ...
The original post asks if you are worrying about your heart. But, to be a little more precise you may need to reword the question to include vascular health as well.
I am only guessing, but I would suggest that
coronary blood vessel health is a major factor in "active sudden death" scenarios. Many other heart diseases are considerably more "self-limiting" is as much that they cause fatigue or shortness of breath before the subject can exercise to death.
How many of the previous posters have undergone cardiac catheterization and are reasonably sure of healthy heart vessels? If not - then you have some cause for concern when you start maxing out, especially at an older age, or a history of smoking or obesity.