1. From the Division of Cardiology (H.E.P., H.-K.K., D.-H.S., J.-H.K., M.K.S., Y.-J.K., G.-Y.C., D.-W.S., B.-H.O., Y.-B.P.), Department of Internal Medicine, Cardiovascular Center, Seoul National University Hospital; and the Division of Cardiology (S.-A.C.), Department of Internal Medicine, Cardiac and Vascular Center, Samsung Medical Center, Seoul, Korea.