From the Department of Cardiology, Cardiff University (J.P.J.H.); Vascular Physiology Unit, Institute of Child Health (J.P.J.H., A.E.D., E.E., J.E.D.); and Department of Epidemiology and Public Health, University College (D.R.W., M.J.S., E.J.B., M.G.M.), London, UK. (At 2009-02-24)