1 Cardiovascular Division, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts. Electronic address: abuxton@bidmc.harvard.edu.
2 Cardiovascular Division, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts.
3 Krannert Institute of Cardiology, Indiana University School of Medicine, Indianapolis, Indiana.
4 Cardiovascular Division, Department of Medicine, Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania.