1. Division of Cardiology, Asan Medical Center, College of Medicine, University of Ulsan, Seoul, Korea (D.-H.K., S.L., M.-S.K., J.-M.S., J.-J.K.).
2. Division of Cardiology, Samsung Medical Center, Seoul, Korea (S.-J.P., S.-W.P.).
3. Division of Cardiology, Inha University Medical Center, Incheon, Korea (S.-H.S.).
4. Division of Cardiology, Severance Medical Center, Seoul, Korea (G.-R.H.).
5. Division of Clinical Epidemiology and Biostatistics, Asan Medical Center, College of Medicine, University of Ulsan, Seoul, Korea (S.-C.Y.).