1. The Korean Cardiac Research Foundation, Seoul, Korea.
2. Division of Cardiology, Department of Internal Medicine, Inje University Sanggye Paik Hospital, Seoul, Korea.
3. Department of Internal Medicine, College of Medicine, Chungbuk National University, Chungbuk National University Hospital, Cheongju, Korea.
4. Department of Internal Medicine, Kangdong Sacred Heart Hospital, Hallym University Medical Center, Seoul, Korea.