1. From the Department of Medicine/Cardiology, Johns Hopkins University School of Medicine, Baltimore, MD (T.S., R.H., M.M.Z., A.K., R.D.B., H.C., H.R.H., S.N.); and Radiology and Imaging Sciences, NIH Clinical Center, National Institute of Biomedical Imaging and Bioengineering, Bethesda, MD (D.A.B.).