[1] Yorkhill Hosp, Dept Paediat Cardiothorac Surg, Glasgow, Lanark, Scotland
[2] Univ Edinburgh, Royal Infirm Edinburgh, Dept Haematol, Edinburgh, Midlothian, Scotland
[3] Univ Edinburgh, Royal Infirm Edinburgh, Dept Cardiothorac Surg, Edinburgh, Midlothian, Scotland