1. From the Cardiovascular Magnetic Resonance Unit and the NIHR Cardiovascular Biomedical Research Unit, Royal Brompton Hospital and Imperial College, London, UK (J.P., A.J.B., S.K.P., D.J.P, P.J.K.); the National Heart and Lung Institute, Imperial College, London, UK (A.J.B., S.K.P., D.J.P., P.J.K.); and the Institute of Cardiology, Warsaw, Poland (J.P.).