[1] Univ Cape Town, Dept Hlth & Rehabil Sci, Div Commun Sci & Disorders, Cape Town, South Africa
[2] Univ Cape Town, Dept Paediat & Child Hlth, Cape Town, South Africa
[3] Univ Cape Town, Red Cross Childrens Hosp, Dept Paediat & Child Hlth, Div Paediat Cardiol, Cape Town, South Africa
[4] Univ Cape Town, Groote Schuur Hosp, Dept Med, Div Cardiol, Cape Town, South Africa