1. Cardiology Department, Washington DC Veterans Affairs Medical Center, 50 Irving Street NW, Washington, DC 20422, USA
2. School of Medicine Georgetown University, 4000 Reservoir Road NW, Washington, DC 20007, USA
3. School of Medicine and Health Care Sciences, George Washington University, Washington, DC 20052, USA
4. Washington DC Veterans Affairs Medical Center, 50 Irving Street NW, Washington, DC 20422, USA