Non-linear analysis of atrial signals for assessing the effects of adrenergic activation in sinus rhythm and atrial fibrillation

Aim of this study is to understand the effects of sympathetic nervous system stimulation during atrial fibrillation. A non-linear analysis is presented and used to characterize the dynamics in both intra-atrial signals (atrial electrograms) and Local Atrial Period (LAP) series. In particular, the level of organization between two electrograms or two LAP series was assessed by the synchronization index (S), based on the corrected cross-conditional entropy. Besides, the degree of recurrence of a pattern in a signal was defined by the regularity index (R), based on the estimation of corrected conditional entropy. Adrenergic activation was induced by infusing small doses of isoproterenol. The parameters obtained from both analysis underline a trend of reduction of spatial organization after isoproterenol administration both in sinus rhythm and in atrial fibrillation