Department of Cardiology, Odense University Hospital, Odense, Denmark. Electronic address: okkels@dadlnet.dk. Department of Cardiology, Aarhus University Hospital, Skejby Hospital, Aarhus, Denmark. Department of Cardiology, Aalborg University Hospital, Aalborg, Denmark. Department of Clinical Epidemiology, Aarhus University, Aarhus, Denmark. Department of Cardiology, Odense University Hospital, Odense, Denmark. Department of Cardiology, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.