I've been doing some research on heart conditions and now I'm confused on a much higher level. :) I'm looking for a specific heart problem and I think thre may be different conditions out there that can cover this, so I'll explain the situation and how I want it to inflict the character.
The character is a boy aged 17. He was fat throughout his childhood but in seventh grade he dieted extensively and became physically fit. He discovered his genes work like his father's, meaning that they start out fat but end up with great metabolisms and can eat anything. When his father died his freshman year, he dieted dangerously to the point of becoming underweight (not anorexic, just kind of going through depressed atrophy). He played football but quit when he collapsed on the field and was told that he should stop playing sports. Then in his senior year he is arguing with his best friend when he has a heart attack and is sent to the hospital for it whre they may (or may not, depending on a disease given) have gone through with surgery.
I've been toying with the idea of bradycardia, an overlarge heart or maybe a hole in the heart, but that's the best I can come up with. I know that bradycardia has to do with electricity in the heart, but the only surgery I can see for that would be for a pace maker, so I was just wondering if someone had a better idea of possible condition. Play doctor, or change the thing some, I'm open.