1. Department of Cardiovascular Medicine and Radiology, Brigham and Women's Hospital, Harvard Medical School, 75 Francis St., Boston, MA 02115, USA
2. Department of Medicine, Division of Cardiovascular Disease, University of Alabama at Birmingham, 1900 University Boulevard Birmingham, AL 35233, USA
3. Department of Medicine, Cardiovascular Division, University of Minnesota, 420 Delaware St SE, Minneapolis, MN 55455, USA
4. Department of Medicine, University of Alabama at Birmingham, 1808 7th Ave South, Birmingham, AL 35233, USA
5. Department of Neurology, University of Alabama at Birmingham, 1720 2nd Ave South, Birmingham, AL 35294, USA
6. Department of Veterans Affairs, Section of Cardiology, Birmingham Veterans Affairs Medical Center, 1720 2nd Ave South, Birmingham, AL 35294, USA