1 Department of Echocardiography, Harefield Hospital, Guy's and St. Thomas' NHS Foundation Trust, London, United Kingdom; National Heart and Lung Institute, Imperial College London, United Kingdom.
2 Adult Congenital Heart Centre and Centre for Pulmonary Hypertension, Royal Brompton Hospital, Guy's and St Thomas' NHS Foundation Trust, London, United Kingdom; National Heart & Lung Institute, Imperial College London, United Kingdom.
3 Department of Echocardiography, Harefield Hospital, Guy's and St. Thomas' NHS Foundation Trust, London, United Kingdom.
4 Department of Echocardiography, Royal Brompton Hospital, Guy's and St. Thomas' NHS Foundation Trust, London, United Kingdom.
5 Department of Echocardiography, Royal Brompton Hospital, Guy's and St. Thomas' NHS Foundation Trust, London, United Kingdom; National Heart and Lung Institute, Imperial College London, United Kingdom.