1. Division of Cardiology, Severance Cardiovascular Hospital, Yonsei University College of Medicine, Seoul, Korea.
2. Division of Cardiology, Gangam Severance Hospital, Yonsei University College of Medicine, Seoul, Korea.
3. Division of Cardiology, Gil Medical Center, Incheon, Korea.
4. Division of Cardiology, Bundang Cha Hospital, Seongnam, Korea.
5. Division of Cardiology, Myongji Hospital, Goyang, Korea.
6. Division of Cardiology, Kangnam Sacred Heart Hospital, Seoul, Korea.