1. From the Centre for Cardiovascular Science, University of Edinburgh, Edinburgh, United Kingdom (P.T.L., M.R.D., A.S.); Scottish National Advanced Heart Failure Service, Golden Jubilee National Hospital, Glasgow, United Kingdom (S.P., J.R.P.); Cardiovascular Genetics, University College London, London, United Kingdom (S.E.H.); Royal Brompton Hospital, Imperial College, London, United Kingdom (D.J.P.); Institute for Human Health and Performance, University College London, London, United Kingdom (H.E.M.).