What causes teens ages 13 on up into there early 20s to die while performing a?

Usually(at least from my understanding) it is an undetected congenital heart defect such as a valve problem(like aortic stenosis) its sad because CHD's are so under funded and so little awareness that these kids are living life with an undetected congenital heart defect that can kill them. Congenital heart defects occur in 1 out of every 100 babies. a CHD means you are born with something wrong with your heart. There is no cure for CHD but you can treat them with meds and surgeries. So if the defect isnt caught soon enough then it can cause horrible consequences(such as heart failure and death)