1. From the Division of Clinical Pharmacology, Department of Medicine (M.F., E.S.-G., H.S.H., B.C.K.), Division of Cardiology, Department of Medicine (E.S.-G., D.D.), Department of Biomedical Engineering and Physics (R.V.), and Division of Cardiology, Department of Pediatrics (P.J.K.), Vanderbilt University, Nashville, TN; and Department of Cardiovascular Diseases, University of Pisa, Pisa, Italy (M.F.).