1. Department of Internal Medicine, Inje University College of Medicine, Busan 614-735, South Korea
2. Department of Internal Medicine, Seoul National University College of Medicine, Seoul 156-707, South Korea
3. Cardiovascular Center, Seoul National University Bundang Hospital, Seoul 110-799, South Korea
4. Seoul National University Boramae Medical Center, Seongnam-si, Gyeonggi-do 463-707, South Korea
5. Cardiovascular Center, Seoul National University Boramae Medical Center, Shindaebang 2-Dong 425, Dongjak-Gu, Seoul 110-779, South Korea
6. Cardiovascular Center, Seoul National University Hospital, Seoul 110-799, South Korea