1. South Africa MRC unit on Child and Adolescent Health Department of Paediatrics and Child Health Red Cross War Memorial Children's Hospital University of Cape Town Cape Town South Africa
2. Division of Paediatric Cardiology Department of Paediatrics and Child Health Red Cross War Memorial Children's Hospital University of Cape Town Cape Town South Africa
3. Division of Cardiology Department of Medicine Groote Schuur Hospital Faculty of Health Sciences University of Cape Town Cape Town South Africa
4. Department of Paediatrics and Child Health Stellenbosch University Matieland South Africa
5. Division of Epidemiology & Biostatistics School of Public Health & Family Medicine University of Cape Town Cape Town South Africa