1. Division of Cardiology, Department of Internal Medicine, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea.
2. Division of Cardiology, Cardiovascular Center, Keimyung University Dongsan Hospital, Daegu, Korea.
3. Division of Cardiothoracic surgery, Cardiovascular Center, Keimyung University Dongsan Hospital, Daegu, Korea.