1. Department of Emergency Medicine, Center for Vascular Emergencies, Massachusetts General Hospital, 0 Emerson Place, MA 02114, USA
2. Department of Cardiology, Aarhus University Hospital, Palle Juul Jensens Boulevard 99, 8200, Aarhus N, Denmark
3. Department of Cardiology, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114, USA
4. Biostatistics Center, Massachusetts General Hospital, 50 Staniford Street, Boston, MA 02114, USA