1. Department of Cardiac Surgery, Royal Brompton and Harefield Hospital , England, UK
2. Department of Cardiothoracic Surgery, Castle Hill Hospital, Cottingham , England, UK
3. Department of Cardiac Surgery, Queen Elizabeth University Hospital , Birmingham, UK
4. Michigan Society of Thoracic and Cardiovascular Surgery Quality Collaborative , Ann Arbor, MI, USA
5. Department of Cardiothoracic Surgery, University Medical Center , Utrecht, Netherlands
6. Department of Cardiothoracic Surgery, Barts Health NHS Trust, St Bartholomew’s hospital , London, UK
7. Department of Cardiothoracic Surgery, University Hospital of Cologne , Cologne, Germany
8. Department of Cardiac Surgery, Medical University of Innsbruck , Innsbruck, Austria
9. Department of Cardiac Surgery, University of Angers , Angers, France
10. Division of Cardiovascular and Thoracic Surgery, Duke University , Durham, NC, USA
11. Cardiothoracic Surgery Department, Centro Hospitalar Universitário São João , Porto, Portugal
12. University Department for Cardiac Surgery, Leipzig Heart Center, University of Leipzig , Leipzig, Germany
13. Department of Cardiac Surgery, Hospital Universitario de Navarra , Pamplona, Spain