1. From the Cardiovascular Division (R.T.L.), Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston, Mass; the Center for Biomedical Engineering (H.Y., R.D.K., R.T.L.), Massachusetts Institute of Technology, Cambridge, Mass; the Health Sciences and Technology Division of the Massachusetts Institute of Technology (H.H.), Cambridge, Mass; and the Department of Cardiovascular Pathology (R.V., A.P.B.), Armed Forces Institute of Pathology, Washington, DC.