1 Department of Surgery, Dutch Institute for Clinical Auditing, Leiden, The Netherlands; Leiden University Medical Center, and the Scientific Bureau, Dutch Institute for Clinical Auditing, Leiden, The Netherlands. Electronic address: f.hoeijmakers@lumc.nl.
2 Department of Surgery and Department of Cardiothoracic Surgery, Amsterdam UMC, VU University Medical Center, Amsterdam, The Netherlands.
3 Department of Surgery, Northwest Clinics, Alkmaar, The Netherlands.