[1] Papworth Hosp, Pulm Vasc Dis Unit, Cambridge CB23 3RE, England
[2] Royal Hallamshire Hosp, Pulm Vasc Dis Unit, Sheffield S10 2JF, S Yorkshire, England
[3] Hammersmith Hosp, Dept Cardiol, London, England
[4] Freeman Rd Hosp, No Pulm Vasc Unit, Newcastle Upon Tyne NE7 7DN, Tyne & Wear, England
[5] Univ Newcastle Upon Tyne, Inst Cellular Med, Newcastle Upon Tyne NE1 7RU, Tyne & Wear, England
[6] Univ Glasgow, Western Infirm, Scottish Pulm Vasc Unit, Glasgow G11 6NT, Lanark, Scotland
[7] Royal Free Hosp, Dept Cardiol, London NW3 2QG, England