1. From the Department of Cardiovascular Medicine (B.M.M., F.R.G., M.F., H.W.), University of Oxford, Oxford, United Kingdom; The Cardiac Clinic (B.M.M.), Department of Medicine, University of Cape Town, South Africa; School of Mathematics and Statistics (P.J.A.) and Institute of Human Genetics (M.B., N.G., H.I., B.K.), University of Newcastle upon Tyne, United Kingdom.