Department of Medicine, Massachusetts General Hospital, Boston, MA. Cardiology Division, Department of Medicine, Massachusetts General Hospital, Boston, MA. Division of Pulmonary, Critical Care, and Sleep Medicine, North Shore Medical Center, Salem, MA. Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, MA; Heart Center Intensive Care Unit, Massachusetts General Hospital, Boston, MA; Smith Center for Outcomes Research in Cardiology, Division of Cardiovascular Medicine, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA. Cardiology Division, Department of Medicine, Massachusetts General Hospital, Boston, MA; Heart Center Intensive Care Unit, Massachusetts General Hospital, Boston, MA. Electronic address: mgsilverman@mgh.harvard.edu.