1 Department of Cardiology, Boston Children's Hospital, Boston, Massachusetts; Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts.
2 Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts.
3 Divisions of Cardiology and Clinical Epidemiology, Jewish General Hospital, McGill University, Montreal, Quebec, Canada.
4 Department of Medicine, Temple University School of Medicine, Philadelphia, Pennsylvania.