[1] Royal Brompton Hosp, Clin Trials & Evaluat Unit, London SW3 6NP, England
[2] Univ London Imperial Coll Sci Technol & Med, Natl Heart & Lung Inst, London, England
[3] Royal Infirm Edinburgh NHS Trust, Edinburgh, Midlothian, Scotland
[4] Royal Alexandra Hosp, Paisley, Renfrew, Scotland
[5] Aintree Univ Hosp NHS Fdn Trust, Liverpool, Merseyside, England
[6] Birmingham Heartlands Hosp, Birmingham B9 5ST, W Midlands, England
[7] Walsgrave Gen Hosp, Coventry CV2 2DY, W Midlands, England