1. First Cardiology Clinic, Medical School, National and Kapodistrian University of Athens, Hippokration Hospital, Athens, Greece
2. 2ndPropedeutic Department of Internal Medicine, Aristotle University, Thessaloniki, Greece
3. Klinik furInnereMedizin III, Universitatsklinikum des Saarlandes, Homburg/Saar, Germany
4. Veteran Affairs Medical Center and Georgetown University, Washington, D.C, United States