1. From the Division of Clinical Pharmacology, Department of Medicine (M.F., H.S.H., P.J.K., B.C.K.), Division of Cardiology, Department of Pediatrics (P.J.K.), Vanderbilt University Medical School, Nashville, TN; and Department of Clinical and Experimental Cardiology, Academic Medical Center, Amsterdam, the Netherlands (C.v.d.W., I.N., A.A.M.W.).