Thank you for chosing heart disease forum for your question. Your question has had responses from previous posts and the correct forum, however, there is a new forum that relates specifically to congenital heart disorders.
http://www.medhelp.org/forums/Pediatric-Cardiology/show/302
But of interest for you and some insight, researchers in Argentina found that patients with keratoconus (a hereditary, degenerative condition that causes the cornea to thin and protrude into a cone-like shape) were more likely to be deficient in magnesium. Interestingly, one of the researchers from this study also noticed the links between Mg deficits, keratoconus and Marfan and Down syndrome.
Though some cases have traced causes to heredity, others to injury, and yet others to diseases or medical disorders such as Down's Syndrome, Ehlers-Danlos Syndrome, Marfan's Syndrome, and Addison's Disease. In some cases, keratoconus has been linked to excessive eye rubbing and long-term use of hard contact lenses. The etiology of keratoconus is still unknown.
Because the syndrome can be of medical significance at a young age, I have suggested you post your question with the pediatric heart community as that is a new group that has experience and knowledge with congenital heart disease, and its association with other health complications and the community can identify with your medical situation.
Thanks for sharing, and I wish you well going forward. Hope we can be of help for you. Take care,
Ken