1. Division of Cardiology, Department of Internal Medicine, Kyungpook National University Hospital, Daegu, Korea.
2. Department of Internal Medicine, School of Medicine, Kyungpook National University, Daegu, Korea.
3. Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Kyungpook National University Hospital, School of Medicine, Kyungpook National University, Daegu, Korea.