1. Cardiovascular Division, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard-Thorndike Electrophysiology Institute, Harvard Medical School, Boston, MA (M.B., M.R., E.L., A.E.B., E.A.).
2. Division of Cardiovascular Medicine, Richard A. and Susan F. Smith Center for Cardiovascular Outcomes Research, Beth Israel Deaconess Medical Center, Boston, MA (C.S.).