1. Heart Research Follow-up Program; University of Rochester Medical Center; Rochester NY USA
2. Department of Cardiology; Gentofte University Hospital; Hellerup Denmark
3. Department of Cardiology; Bispebjerg Hospital; Copenhagen Denmark
4. Department of Cardiology; Rigshospitalet; Copenhagen Denmark
5. Arrhythmia Institute; Valley Health System New York; New York Ridgewood NJ USA
6. Cardiology Division; Department of Medicine and Duke Clinical Research Institute; Duke University Medical Center; Durham NC USA