[1] Asklepios Clin Altona, D-22763 Hamburg, Germany
[2] Krankenhaus Neuwerk Monchengladbach, Hamburg, Germany
[3] Kreiskrankenhaus Traunstein, Hamburg, Germany
[4] Marienhosp Stuttgart, Hamburg, Germany
[5] Charite, Inst Biometrie & Klin Epidemiol, D-13353 Berlin, Germany
[6] Charite, Univ Klin Allgemein Visceral Gefass & Thoraxchiru, D-13353 Berlin, Germany