1. Aristotle University of Thessaloniki, Greece
2. 251 HAF and VA Hospital, Athens, Greece
3. Division of Cardiology, Medstar Washington Hospital Center, Washington, DC, USA
4. Department of Neurosurgery, Vanderbilt University Hospital, Nashville, TN, USA
5. Department of Neurosurgery, Thomas Jefferson University, Philadelphia, PA, USA
6. Division of Cardiology, Denver VA Medical Center, University of Colorado, Denver, CO, USA
7. Department of Medicine, Jacobi Medical Center, Albert Einstein College of Medicine, Bronx, NY, USA