1. From the Heart Institute, Good Samaritan Hospital, and University of Southern California, Los Angeles (R.A.K.); University of Louisville (R.B.), Louisville, Ky; Johns Hopkins University (E.M.), Baltimore, Md; Harvard Medical School, Brigham and Women’s Hospital (E.B.), Boston, Mass; and the National Heart, Lung, and Blood Institute (L.R.), Bethesda, Md.