1. Department of Internal Medicine and Cardiovascular Center, Seoul National University Hospital, Seoul, Korea.
2. Division of Cardiology, Department of Internal Medicine, Heart Vascular Stroke Institute, Samsung Medical Center, Seoul, Korea.
3. Department of Internal Medicine, Seoul National University Hospital, Seoul, Korea.
4. Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Seoul National University Bundang Hospital, Seongnam, Korea.