[1] Univ Oxford, Ctr Clin Magnet Resonance Res, Oxford OX1 2JD, England
[2] Univ Oxford, Clin Trials Unit, Oxford OX1 2JD, England
[3] John Radcliffe Hosp, Dept Cardiol, Oxford OX3 9DU, England
[4] Flinders Med Ctr, Dept Cardiovasc Med, Adelaide, SA, Australia
[5] Oregon Hlth & Sci Univ, Adv Imaging Res Ctr, Portland, OR USA