1. From the Adult Congenital Heart Program, Department of Cardiology, Royal Brompton Hospital (G.-P.D., K.D., W.L., S.V.B.-N., C.S.B., B.J., B.B., M.J.M., M.A.G.); Department of Clinical Cardiology, National Heart and Lung Institute, Imperial College (G.-P.D., D.O., P.A.P.-W.); and Cardiac Performance Unit, Department of Cardiology, St Mary’s Hospital (D.P.F.), London, UK.