1. From the Cardiovascular Division, Department of Medicine (M.D.H., E.P.G., R.B., M.P.R., F.C.G., S.D., D.L., W.S.T., J.M.C., R.J.V., D.J.C., F.E.M.) and Department of Radiology (B.D.), University of Pennsylvania School of Medicine, Philadelphia, PA.