1. Cardiac Electrophysiology Section, Department of Cardiovascular Medicine, Cleveland Clinic, OH (H.Y., E.A.).
2. Harvard-Thorndike Electrophysiology Institute, Cardiovascular Division, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston (A.S.-D., M.B., J.S., D.S.).
3. Harvard-CBSET, Department of Pathology, Lexington, MA (R.M.).