Department of Cardiology, Cardiovascular Center, Korea University Anam Hospital, Seoul, Republic of Korea. Division of Cardiology, Department of Internal Medicine, Korea University Ansan Hospital, Ansan, Republic of Korea. Division of Cardiology, Department of Internal Medicine, Bundang CHA Hospital, CHA University College of Medicine, Seongnam, Republic of Korea. Division of Cardiology, Department of Internal Medicine, Seoul Medical Center, Seoul, Republic of Korea. Cardiovascular Department of Internal Medicine, Kyung Hee University Hospital, Seoul, Republic of Korea. Division of Cardiology, Department of Internal Medicine, Bundang Jesaeng Hospital, Seongnam, Republic of Korea. Division of Cardiology, Department of Internal Medicine, Yonsei University Wonju College of Medicine, Wonju, Republic of Korea. Division of Cardiology, Department of Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea. Cardiovascular Center, Korea University Guro Hospital, Seoul, Republic of Korea. Department of Cardiology, Ajou University Medical Center, Suwon, Republic of Korea. Division of Cardiology, Department of Internal Medicine, Kangdong Sacred Heart Hospital, College of Medicine, Hallym University, Seoul, Republic of Korea. Division of Cardiology, Department of Internal Medicine, The Catholic University, Seoul, Republic of Korea. Division of Cardiology, Department of Internal Medicine, Soonchunhyang University Hospital, Seoul, Republic of Korea. Division of Cardiology, Department of Internal Medicine, Medical Research Institute, Pusan National University Hospital, Busan, Republic of Korea. Division of Cardiology Heart Center, Konyang University Hospital, Daejeon. Cardiovascular Center, Dongguk University Ilsan Hospital, Goyang, Republic of Korea. Division of Cardiology, Department of Internal Medicine, Inha University Hospital, Incheon, Republic of Korea. Division of Cardiology, Department of Internal Medicine, NHIS Ilsan Hospital, Goyang, Republic of Korea. Division of Cardiology, Department of Internal Medicine, The Catholic University of Korea St. Vincent's Hospital, Suwon, Republic of Korea. Division of Cardiology, Department of Internal Medicine, Seoul National University Hospital, Seoul National University College of Medicine, Seoul, Republic of Korea. Electronic address: usahyosoo@gmail.com.