Abstract 634: Sympathetic Stimulation And Vagal Inhibition Have Opposite Effects On The Frequency Spectrum Of AF
Introduction & Hypothesis Animal models of atrial fibrillation (AF) suggest that the autonomic nervous system (ANS) is involved in the pathophysiology of AF. We hypothesize that sympathetic stimulation with isoprenaline and vagal blockade with atropine will produce changes in spectral frequency of human AF Methods 10 patients (all had persistent AF) who were in AF at the start of catheter ablation for AF were studied. 5 of these patients received intravenous isoprenaline infusion first (2 microgram/min). After stopping isoprenaline and allowing heart rate to return to baseline, atropine (1mg)was given. The remaining 5 received atropine only Mean organization index (OI) and dominant frequency (DF), averaged from coronary sinus electrograms recorded by a decapolar catheter over 30s, were obtained by Fast Fourier Transform, before and after giving each drug. Mean ventricular rate (VR) was calculated over 1 minute at each stage.
Results Isoprenaline increased mean DF measured in the coronary sinus, from 7.11 ± 0.57 to 7.89 ± 0.97 Hz (p=0.035), with mean VR increase of 53 ±16%. Atropine reduced mean DF from 6.86± 0.71 to 6.43±0.60 Hz (p=0.008), with mean VR increase of 42 ± 21%. There was no significant difference in VR increase between isoprenaline and atropine (p=0.32). Neither isoprenaline nor atropine induced a significant change in the OI [0.22±0.03 to 0.24±0.03 (p=0.32) and 0.26±0.05 to 0.28±0.05 (p=0.15)]
Conclusion Isoprenaline and atropine have opposite effects on the atrial activation frequency while increasing VR to a similar extent. This shows that the ANS can dynamically influence human AF and provides supportive evidence for targeting ablation at autonomic ganglia