1. From the Montreal Heart Institute and University of Montreal (L.C.), Canada; The Maryland Medical Research Institute (G.L.K., S.A.F.), Baltimore, Md; The National Heart, Lung, and Blood Institute (M.D., N.L.G., Y.R.), Bethesda, Md; University of Minnesota (D.B.H., C.W.W.), Minneapolis; Minneapolis Heart Institute Foundation (F.L.G.), Minn; Cleveland Clinic Foundation (B.J.H.), Ohio; Cedars-Sinai Medical Center (J.S.F.), Los Angeles, Calif; and Baylor College of Medicine (J.A.H.), Houston, Tex.