My cardiologist recently confirmed that my heart is in great shape (I did 19 minutes on a modified Bruce treadmill stress test recently) and will probably never be an issue for me. He said something to the effect of -
"quit worrying about your heart - it is in great shape and you'll surely die from some of the other dumb stuff you do but never from a heart problem"
I feel great most of the time. The problem is just that I feel like I am not getting enough oxygen when working hard.