[1] Queens Univ Belfast, Sch Med, Dept Med, Belfast, Antrim, North Ireland
[2] Alder Hey Children Hosp, Dept Paediat Cardiac Surg, Liverpool, Merseyside, England
[3] Assiut Univ Hosp, Dept Cardiothorac Surg, Assiut, Egypt
[4] Univ Liverpool, Liverpool Ctr Cardiovasc Sci, Liverpool, Merseyside, England
[5] Liverpool Heart & Chest Hosp, Liverpool, Merseyside, England
[6] Liverpool Heart & Chest Hosp, Dept Cardiothorac Surg, Liverpool, Merseyside, England