1. From the Cardiovascular Division, Brigham and Women's Hospital, Harvard Medical School, Boston, MA (Y.S.C., G.K.S., K.C.K., M.I.P., G.-P.S., P.L., C.L.F., E.R.E., P.H.S.); Harvard–MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA (Y.S.C., A.B.B., K.C.K., R.B., M.J., B.V.S., E.R.E.); Mechanical and Industrial Engineering, Northeastern University, Boston, MA (A.U.C.); and Department of Health Services, University of Washington, Seattle (C.M.).