1. From the Departments of Medicine and Radiology (S.N., M.H., M.C., K.H., W.P., T.P., G.E., D.H., K.K.), Würzburg University, Germany; the Cardiac Computer Center, Massachusetts General Hospital, Boston (J.B.N.); and the NMR Laboratory for Physiological Chemistry (J.S.I.), Harvard Medical School, Boston Mass. Dr Ertl’s present address is II Medizinischen Klinik, Klinikum Mannheim, Universität Heidelberg, Theodor-Kutzer-Ufer, 68135 Mannheim, Germany.