[1] Royal Brompton Hosp, Adult Congenital Heart Ctr, London SW3 6NP, England
[2] Royal Brompton Hosp, Ctr Pulm Hypertens, London SW3 6NP, England
[3] Univ London Imperial Coll Sci Technol & Med, Natl Heart & Lung Inst, London, England
[4] Queens Univ, Cardiovasc Lab, Kingston Gen Hosp, Div Cardiol, Kingston, ON, Canada
[5] Univ London Imperial Coll Sci Technol & Med, Natl Heart & Lung Inst, London, England
[6] Royal Brompton Hosp, London, England