1. From the Department of Surgery (J.D.P., C.A.M.) and the Department of Medicine (J.G.R.), Duke University Medical Center, Durham, NC; the Department of Surgery (C.T.K.), University of Florida, Gainesville, FL; the Department of Surgery (R.J.) University of Minnesota, Minneapolis, MN; the Department of Surgery (F.D.P.), University of Michigan, Ann Arbor, MI; and Thoratec Corporation (D.J.F.), Pleasanton, CA.