[1] Univ Tubingen Hosp, Dept Cardiothorac & Vasc Surg, Tubingen, Germany
[2] Johannes Gutenberg Univ Mainz, Med Ctr, Dept Cardiothorac & Vasc Surg, D-55131 Mainz, Germany
[3] Univ Leipzig, Leipzig Heart Ctr, Dept Cardiac Surg, Leipzig, Germany
[4] Univ Hosp Birmingham NHS Trust, Queen Elizabeth Hosp, Dept Cardiac Surg, Birmingham, W Midlands, England
[5] Univ Birmingham, Birmingham, W Midlands, England
[6] Univ Hosp Bern, Dept Cardiovasc Surg, CH-3010 Bern, Switzerland