1. From the Cardiac Arrhythmia Service (S.M.S., V.Y.R.), Pediatric Cardiology (B.A.L.), and Anesthesiology (A.J.C.M.), Mount Sinai School of Medicine, New York, NY; and Cardiology Department, Homolka Hospital, Prague, Czech Republic (P.N., J.S., R.K., J.P., V.Y.R.).