1. From the Departments of Genetics (K.Y.v.S.-Z., J.P.v.T., J.D.H.J.) and Cardiology (D.J.v.V., R.v.d.W., M.P.v.d.B.), University Medical Centre Groningen, University of Groningen, Groningen; Department of Physiology, Free University Medical Centre, Amsterdam (W.J.P.); and Department of Genetics, Erasmus Medical Centre, Rotterdam (D.D.), the Netherlands.