1. Division of Cardiology, Duke University Medical Center, Durham, NC (V.N.R., R.J.M., A.C.C., M.D.K., M.F., A.D.D.).
2. Duke Clinical Research Institute, Duke University School of Medicine, Durham, NC (V.N.R., R.J.M., M.D.K., M.F., R.A.M., A.D.D.).
3. Division of Cardiology, Department of Medicine, University of California at Los Angeles (G.C.F.).
4. Joint Department of Biomedical Engineering, University of North Carolina and North Carolina State University, Chapel Hill (M.C.C.).