1. Department of Cardiac Surgery Hospital Universitario “12 de Octubre” Madrid Spain
2. Department of Cardiac Surgery Hospital Universitario “Alvaro Cunqueiro” Vigo Spain
3. Department of Cardiovascular Surgery, Hospital Clinic University of Barcelona Barcelona Spain
4. Clinic for Cardiac Surgery University Hospital Zürich Zürich Switzerland
5. Department of Cardiothoracic Surgery University of the Free State Bloemfontein South Africa