1. From the Duke Cardiovascular Magnetic Resonance Center (M.R.P., P.J.C., J.F.H., I.K., M.A.P., W.A.J., J.B.W., M.D.E., H.W.K., R.M.J., R.J.K.), Department of Medicine (M.R.P., J.F.H., I.K., M.A.P., T.J.M., J.B.W., M.D.E., H.W.K., R.M.J., R.J.K.), and Department of Radiology (R.M.J., R.J.K.), Duke University Medical Center, Durham, NC.