[1] Royal Brompton & Harefield NHS Trust, Clin Trials & Evaluat Unit, London SW3 6NP, England
[2] Royal Brompton Hosp, Dept Cardiol, London SW3 6LY, England
[3] Univ London Imperial Coll Sci Technol & Med, Natl Heart & Lung Inst, London, England
[4] Royal Victoria Hosp, Belfast BT12 6BA, Antrim, North Ireland
[5] Royal Infirm, Edinburgh, Midlothian, Scotland