1. Department of Medicine, Albert Einstein Medical Center , Philadelphia, PA 19141 , USA
2. Section of Cardiology, Baylor College of Medicine , Houston, TX 77030 , USA
3. Division of Cardiology, Henry Ford Hospital , Detroit, MI 48202 , USA
4. Division of Cardiology, Department of Medicine, Emory University School of Medicine , Atlanta, GA 30322 , USA
5. Section of Vascular Medicine, Department of Cardiovascular Medicine, Heart Vascular and Thoracic Institute, Cleveland Clinic Foundation , Cleveland, OH 44195 , USA
6. Division of Cardiology, Massachusetts General Hospital , Boston, MA 02114 , USA
7. Keele Cardiovascular Research Group, Centre for Prognosis Research, Keele University , Keele ST55BG , UK
8. Department of Cardiology, Royal Stoke University Hospital , Stoke-on-Trent ST46QG , UK
9. Division of Cardiovascular Medicine, Gill Heart Institute, University of Kentucky , Lexington, KY 40536 , USA