1. Nuffield Department of Surgical Sciences, University of Oxford, John Radcliffe Hospital , Oxford , UK
2. Department of Cardiothoracic Surgery, Weill Cornell Medicine , New York City, NY , USA
3. Centre for Statistics in Medicine, Nuffield Department of Orthopaedics, Rheumatology & Musculoskeletal Sciences, University of Oxford , Oxford , UK
4. Bristol Heart Institute, School of Clinical Sciences, University of Bristol , Bristol , UK
5. Health Economics Research Centre, Nuffield Department of Population Health, University of Oxford , Oxford , UK
6. Norwich Medical School, University of East Anglia , Norwich , UK