1. University Hospital Southampton; Wessex Cardiothoracic Centre; Tremona Road Southampton UK SO16 6YD
2. University of Edinburgh; Centre for Population Health Sciences; Edinburgh UK EH8 9AG
3. Northern General Hospital; Department of Surgery; Sheffield Teaching Hospitals NHS Trust Herries Road Sheffield Yorkshire UK S5 7AU
4. Herz- u. Kreislaufzentrum Rotenburg; Department of Cardiology and Vascular Diseases; Heinz-Meise-Street 100 Rotenburg Germany D-36199
5. University of Sheffield, ScHARR; School of Health and Related Research; Regent Court, 30 Regent Street Sheffield UK S1 4DA