Very disturbing post. Youngest I've seen was 27, who smoked.
Completely the end of the spectrum, I took care of a 70 yo female who had no complaints, however, if you grilled her extensively, on ROS, she was feeling fatigued on occasion. Office docs got an EKG, which showed she had a STEMI- they booted her out in a heart beat. So, there she was in the ER, no pain, no current fatigue, no nothing, with a beautiful anterior STEMI, She was cathed and got some stents.
I knew a guy in college who was 24, and kept having "indigestion". It became rather severe one day, so his wife decided to drive him to the ER. He arrested on the way, and they couldn't revive him. Wife widowed at 22 years old. He came from one of those families with ridiculously high cholesterol, and heart attacks in their 30's, but for some reason, his parents had never told him to get his checked.