1. Division of Cardiology, Massachusetts General Hospital , 55 Fruit Street, Yawkey 5B, Boston, MA 02114 , USA
2. Cardiovascular Performance Program, Massachusetts General Hospital , 55 Fruit Street, Yawkey 5B, Boston, MA 02114 , USA
3. Sections of Cardiovascular Medicine and Preventive Medicine and Epidemiology, Boston University School of Medicine , Boston, MA 02118 , USA
4. Division of Cardiology, Penn State Hershey Medical Center , Hershey, PA 17033 , USA