the young athletes who drop dead don't have a defect in the a-v node. they have an
enlarged heart, which partially blocks the opening to the
aorta. when the heart beats fast, like when someone is participating in sports, not enough blood is able to escape the heart and get into the aorta out into the body. eventually, with sustained exercise, they will drop dead. this is a rare condition and runs in families.
a young person could suffer from a congenital heart condition. many young women have heart
murmurs, but this is not usually referred to as "heart disease" .
if you are concerned, go to your doctor and have them listen to your heart, and if you can afford it, request they perfom an ekg.