1. From the Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, U.S. Food & Drug Administration, Silver Spring, MD (D.G.S.); Division of Cardiology, Department of Medicine, Johns Hopkins Medical Institutions, Baltimore, MD (N.M., J.M., L.G.T., K.C.W., P.M.S., J.A.C.L.); Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA (R.L.V., B.D.N.); Division of Cardiology, Department of Medicine, Hospital of the University of...