1. From the Division of Nephrology (R.J.J., D.-H.K., J.K., S.W., M.M.) and Texas Children’s Hospital (D.F.), Baylor College of Medicine, Houston, Tex; Merck and Company, Inc (S.K.), West Point, Pa; The Heart Institute of Spokane (K.R.T.), Spokane, Wash; Hospital Universitario and Universidad del Zulia (B.R.-I.), Maracaibo, Venezuela; and Instituto de Cardiologia (J.H.-A.), Mexico City, Mexico.