@sterven
In my defense/defence, I had a "friend" in my first year of high school that had tachycardia who would also sometimes feel her chest different (I don't remember if it was pain or general discomfort). Sheer heart attacks can happen at almost any age, as far as i know.
I don't know if my heart is weak because I've done strong physical effort and the only time my chest hurt was when I was running across the airport like a mad man in winter trying to catch my flight when I was 12-14. Other than that, my only discomfort was exhaustion and sore feet.