1. From the Feinberg Cardiovascular Research Institute, Division of Cardiology, Northwestern University, Chicago, Ill (D.B., G.M.F., S.D.L., M.R.J., W.G.C., F.J.K., R.O.B., M.G.); and Duke Cardiovascular Magnetic Resonance Center, Division of Cardiology, Duke University, Durham, NC (D.J.S., M.P., R.M.J., R.J.K.).