1. First Department of Cardiology, 'Hippokration' Hospital, University of Athens, Medical School, Athens, Greece
2. Department of Cardiology, 'Evaggelismos' General Hospital, Athens, Greece
3. Department of Cardiology, 'KAT' General Hospital, Athens, Greece
4. Department of Cardiology, 'Laiko' General Hospital, Athens, Greece
5. Department of Cardiology, Helena Venizelou Hospital, Athens, Greece
6. Department of Cardiology, Heraklion University Hospital, Crete, Greece