1. From the Division of Cardiology, Department of Medicine, Cedars-Sinai Medical Center (J.-M.C., Y.-H.K., T.-J.W., H.S.K., P.-S.C.), and the Departments of Medicine (Cardiology), Physiology, and Physiological Science (Z.Q., A.G., J.N.W.), UCLA School of Medicine, Los Angeles, Calif.