[1] Univ Zurich Hosp, Cardiovasc Surg Clin, CH-8091 Zurich, Switzerland
[2] Childrens Hosp, Dept Cardiol, Zurich, Switzerland
[3] Univ Zurich, Dept Biostat, Zurich, Switzerland
[4] Univ Zurich Hosp, Dept Cardiovasc Anesthesia, CH-8091 Zurich, Switzerland