Congenital heart problems

‘The heart’ in Down syndrome. The facts
Selikowitz, Mark (2008) Oxford (3rd ed, first publ 1990), ch 7 pp 85-92

‘Heart disease and children with Down syndrome’

Cousineau, Anthony J and Ronald M Lauer (1995) in Van Dyke, DC et al (eds)

Medical and surgical care for children with Down syndrome. A guide for parents.

Topics in Down Syndrome series, Woodbine House, ch 3 pp 34-63

Downs Heart Group (UK) This UK group is dedicated to providing support and information for families whose child with Down syndrome has a heart condition. It includes information relating the different conditions and other associated issues. Also gives details of the Down's Heart Group Online Community, a contact point for families who have a member with Down syndrome and associated congenital heart disease. 

Heartkids Victoria
Information, including a range of fact sheets (see Resources section), and support avenues for families (see also the national organisation:

Royal Children’s Hospital Melbourne, Cardiology Department
The RCH site includes a large collection of fact sheets for families.