Evaluating this process in human AF has been limited by the cumbersome nature of performing serial, invasive electrophysiologic studies. However, modern pacemakers now permit rapid, non-invasive electrophysiologic testing and can also accurately document AHRE, which allows the convenient study of therapy aimed at preventing the progression from AHRE to overt AF. In addition, this group of patients also affords the ability to evaluate the recurrence of AHRE on the progression of structural and electrical remodeling.