1. Department of Internal Medicine, Wonju College of Medicine, Yonsei University, Wonju, Korea.
2. Department of Internal Medicine, Seoul National University Hospital, Seoul, Korea.
3. Department of Internal Medicine, Sungkyunkwan University College of Medicine, Seoul, Korea.
4. Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Korea.
5. Department of Internal Medicine, Seoul National University Bundang Hospital, Seongnam, Korea.
6. Department of Internal Medicine, Heart Research Center of Chonnam National University, Gwangju, Korea.
7. Department of Internal Medicine, Chungbuk National University College of Medicine, Cheongju, Korea.
8. MetroWest Medical Center, Framingham, MA, USA.
9. Department of Biostatics, Wonju College of Medicine, Yonsei University, Wonju, Korea.