1. From the Wallace H. Coulter Department of Biomedical Engineering (J.S., W.R.T., D.P.G.), Georgia Institute of Technology and Emory University; the George W. Woodruff School of Mechanical Engineering (R.E.G.), Georgia Institute of Technology; the Department of Medicine (D.E.F., D.S., W.R.T.), Division of Cardiology, Emory University; and the Atlanta VA Medical Center (W.R.T.), Atlanta, Ga.