Assessment of the dynamics of atrial signals and local atrial period series during atrial fibrillation: effects of isoproterenol administration

Background: The autonomic nervous system (ANS) plays an important role in the genesis and maintenance of atrial fibrillation (AF), but quantification of its electrophysiologic effects is extremely complex and difficult. Aim of the study was to evaluate the capability of linear and non-linear indexes to capture the fine changing dynamics of atrial signals and local atrial period (LAP) series during adrenergic activation induced by isoproterenol (a sympathomimetic drug) infusion. Methods: Nine patients with paroxysmal or persistent AF (aged 60 ± 6) underwent electrophysiological study in which isoproterenol was administered to patients. Atrial electrograms were acquired during i) sinus rhythm (SR); ii) sinus rhythm during isoproterenol (SRISO) administration; iii) atrial fibrillation (AF) and iv) atrial fibrillation during isoproterenol (AFISO) administration. The level of organization between two electrograms was assessed by the synchronization index (S), whereas the degree of recurrence of a pattern in a signal was defined by the regularity index (R). In addition, the level of predictability (LP) and regularity of LAP series were computed. Results: LAP series analysis shows a reduction of both LP and R index during isoproterenol infusion in SR and AF (RSR = 0.75 ± 0.07 RSRISO = 0.69 ± 0.10, p < 0.0001; RAF = 0.31 ± 0.08 RAFISO = 0.26 ± 0.09, p < 0.0001; LPSR = 99.99 ± 0.001 LPSRISO = 99.97 ± 0.03, p < 0.0001; LPAF = 69.46 ± 21.55 LPAFISO = 55 ± 24.75; p < 0.0001). Electrograms analysis shows R index reductions both in SR (RSR = 0.49 ± 0.08 RSRISO = 0.46 ± 0.09 p < 0.0001) and in AF (RAF = 0.29 ± 0.09 RAFISO = 0.28 ± 0.08 n.s.). Conclusions: The proposed parameters succeeded in discriminating the subtle changes due to isoproterenol infusion during both the rhythms especially when considering LAP series analysis. The reduced value of analyzed parameters after isoproterenol administration could reflect an important proarrhythmic influence of adrenergic activation on favoring maintenance of AF.