1. From the Department of Medicine, University of Pittsburgh School of Medicine, PA (E.B.S.); University of Pittsburgh Medical Center, Cardiovascular Magnetic Resonance Center, Heart and Vascular Institute, PA (E.B.S.); Clinical and Translational Science Institute, University of Pittsburgh, PA (E.B.S.); and Barts Heart Centre, London, United Kingdom (J.C.M.); Institute of Cardiovascular Science, University College, London, London, United Kingdom (J.C.M.).