[1] Glenfield Hosp, Dept Cardiac Surg, Groby Rd, Leicester LE3 9QP, Leics, England
[2] Campus Biomed Univ Rome, Dept Cardiovasc Surg, Via Alvaro del Portillo 21, I-00128 Rome, Italy
[3] Helsinki Univ Hosp, Heart & Lung Ctr, POB 340,Haartmaninkatu 4, Helsinki 00029, Finland
[4] Univ Helsinki, POB 340,Haartmaninkatu 4, Helsinki 00029, Finland
[5] Glenfield Hosp, Dept Anaesthesia, Groby Rd, Leicester LE3 9QP, Leics, England