1. From the Evans Department of Medicine (E.J.B., J.F.K., J.A.V.), Whitaker Cardiovascular Institute (E.J.B., R.S.V., J.F.K., J.A.V.), and Preventive Medicine Section (E.J.B., M.G.L., R.S.V.), Boston University School of Medicine, Boston, Mass; Cardiovascular Engineering, Inc (G.F.M.), Holliston, Mass; and the Framingham Study (E.J.B., M.G.L., M.J.K., R.S.V., B.T.L., S.F., E.O.), National Heart, Lung and Blood Institute, Framingham, Mass.