1. Division of Cardiology, Massachusetts General Hospital, Boston (J.E.H., G.D.L).
2. Cardiovascular Research Center (J.E.H., C.N), Massachusetts General Hospital, Harvard Medical School, Charlestown.
3. Martinos Center of Biomedical Imaging (C.N.), Massachusetts General Hospital, Harvard Medical School, Charlestown.
4. Health Science Technology, Massachusetts Institute of Technology, Cambridge (C.N.).