[1] James Cook Univ Hosp, Dept Cardiothorac Surg, Middlesbrough TS4 3BW, Cleveland, England
[2] Univ Liverpool, Dept Biostat, Liverpool L69 3GL, Merseyside, England
[3] UCL, NICOR, London EC1A 4NP, England
[4] Comp Sci Corp, London N1C 4AG, England
[5] Univ Manchester, Univ Hosp South Manchester, Acad Surg Unit, Manchester Acad Hlth Sci Ctr, Manchester M23 9LT, Lancs, England
[6] Bristol Royal Infirm & Gen Hosp, Bristol Heart Inst, Dept Cardiac Surg, Bristol BS2 8HW, Avon, England
[7] Derriford Hosp, South West Cardiothorac Ctr, Plymouth PL6 8DH, Devon, England
[8] Royal Brompton Hosp, Cardiovasc Biomed Res Unit, London SW3 6NP, England
[9] Univ Manchester, Manchester Acad Hlth Sci Ctr, Ctr Hlth Informat, Vaughan House, Manchester M13 9GB, England