1. Department of Medicine, MetroWest Medical Center, Framingham, MA 01702, USA
2. Division of Cardiology, Department of Internal Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul 03181, Republic of Korea
3. Department of Physical Medicine and Rehabilitation, Harvard Medical School/Spaulding Rehabilitation Hospital, Boston, MA 02129, USA
4. Division of Biostatistics, Department of R&D Management, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul 03181, Republic of Korea
5. Division of Cardiology, Department of Internal Medicine, Seoul Eulji Hospital, Eulji University School of Medicine, Seoul 06047, Republic of Korea
6. Department of Internal Medicine, Soonchunhyang University Gumi Hospital, Gumi 39371, Republic of Korea