1 National Heart and Lung Institute, Imperial College London, London, United Kingdom.
2 Columbia University Irving Medical Center/NewYork-Presbyterian Hospital and the Cardiovascular Research Foundation, New York, New York, USA.
3 Department of Cardiology, St Francis Hospital and Heart Center, Roslyn, New York, USA; New York Institute of Technology, Old Westbury, New York, USA.
4 Division of Cardiology, University of California, San Francisco, San Francisco, California, USA. Electronic address: yousif.ahmad@ucsf.edu.