From the Harvard-MIT Division of Health Sciences and Technology (E.R.E., P.S., A.G., D.B., C.R.) and the Department of Mechanical Engineering (A.M.), Massachusetts Institute of Technology, Cambridge, Mass, and the Department of Medicine, Cardiovascular Division, Brigham and Women’s Hospital and Harvard Medical School (E.R.E., C.R.), Boston, Mass. (At 2001-01-23)