Autonomic Modulation of Ventricular Response by Exercise and Antiarrhythmic Drugs during Atrial Fibrillation

Abstract

Ventricular response (VR) during atrial fibrillation (AF) is a complex process that is influenced by the autonomic nervous system (ANS). Although antiarrhythmic drugs are known to have modulating ANS effects, these are not routinely evaluated in the clinical setting. Therefore, the purpose of this study is to characterize VR to exercise as ANS stimulus during AF and to evaluate possible modulating effects of antiarrhythmic drugs (flecainide and amiodarone). Seventeen patients (11 males, mean age 61±11 years), with persistent AF, underwent bicycle exercise testing before and after 3 – 5 days of oral flecainide (9 patients) or amiodarone (8 patients) loading. RR series were derived from ECG recordings and analyzed by means of time domain parameters (mean, SDNN, pNN50 and rMSSD) and non-linear methods assessing the predictability of the time series (level of predictability (P) and regularity (R)). The effect of exercise in VR modulation was evident both with and without antiarrhythmic drugs (p<.05). Both antiarrhythmic drugs had no significant effects at rest but on exercise conditions: flecainide decreased pNN50 and rMSSD, while amiodarone increased the mean of NN interval. In addition, flecainide amplified the response to exercise, resulting in a pronounced pNN50 reduction, while no differences were observed with amiodarone administration. In conclusion, antiarrhythmic drugs exhibit ANS modulating effects during exercise that are not apparent during resting conditions.