1. From the Division of Cardiology, the Department of Medicine (C.W.C., G.S.N., M.T., R.D.B., D.A.K.), the Department of Biomedical Engineering (B.T.W., J.D., E.R.M., D.A.K.), and the Department of Radiology (E.R.M.), The Johns Hopkins Medical Institutions, Baltimore, Md.