1 Cardiology Department, Northwick Park Hospital, London North West University Healthcare NHS Trust, Watford Road, Harrow, London, HA1 3UJ, UK.
2 Cardiac Electrophysiology Group, Cardiology Department, Royal Brompton Hospital, Royal Brompton and Harefield NHS Foundation Trust, Sydney Street, London, SW3 6NP, UK.
3 Structural Heart Disease Group, Cardiology Department, Royal Brompton Hospital, Royal Brompton and Harefield NHS Foundation Trust, Sydney Street, London, SW3 6NP, UK.