1. Veterans Affairs Medical Center, 50 Irving Street NW, Washington, DC, 20422, USA
2. Georgetown University School of Medicine, 4000 Reservoir Road NW, Washington, DC, 20007, USA
3. George Washington University, School of Medicine and Health Sciences, 2121 J Street, NW, Washington, DC, 20052, USA
4. Veterans Affairs Palo Alto Health Care System, 3801 Miranda Ave, Palo Alto, CA, 94304, USA
5. Stanford University, Stanford, CA, USA
6. Asklepeion General Hospitals/Cardiology, Athens, Greece