[1] Univ Maryland, Sch Med, Dept Med, Div Cardiol, Baltimore, MD 21201 USA
[2] Univ Calgary, Calgary, AB T2N 1N4, Canada
[3] Boston Univ, Sch Med, Boston, MA 02118 USA
[4] Royal Prince Alfred Hosp, Dept Cardiol, Sydney, NSW, Australia
[5] Royal Victoria Hosp, Montreal, PQ H3A 1A1, Canada
[6] Brigham & Womens Hosp, Vasc Diagnost Lab, Cardiac Div, Boston, MA 02115 USA
[7] Great Ormond St Hosp Sick Children, Vasc Physiol Unit, London WC1N 3JH, England
[8] Hannover Med Sch, Dept Cardiol & Angiol, Hannover, Germany
[9] Wake Forest Univ, Bowman Gray Sch Med, Dept Internal Med, Winston Salem, NC 27103 USA
[10] Wake Forest Univ, Bowman Gray Sch Med, Dept Cardiol, Winston Salem, NC 27103 USA
[11] UCL, London, England