Abstract 2169: Chronic Intra-cardiac Parasympathetic AV-node Pacing In Goats With Chronic AF To Control Ventricular Rate
INTRODUCTION Drug therapy to reduce the ventricular rate during atrial fibrillation (AF) is effective in only 50% of the patients and limited by side effects. Currently available pacing algorithms are even less effective. The aim of this study was to test the feasibility of chronic AV-Node Inhibition (AVNI) by intra-cardiac parasympathetic nerve stimulation. Our ultimate goal is to develop a pacemaker device with a feature to inhibit AV node function to decrease ventricular rate during AF.
METHODS Leads were implanted in the right atrial appendage and right ventricular apex and connected to a pacemaker for AF induction. In addition, an atrial lead (’AVNI lead’) connected to an implantable high frequency neurostimulator was implanted at a site with a strong prolongation of the PQ-time. Immediately after implantation optimal settings, optimal location, acute effects of AVNI on ventricular rate and the possible pro-arrhythmic effects of AVNI were assessed. The ’safety window’ for AVNI was defined as the difference between the output at the AVNI lead that produced atrial capture and the output that produced AVNI. One week after implantation, AF was maintained for one week by burst pacing via the lead in the right atrial appendage. After this 2 week period, the chronic effects of AVNI were assessed weekly for periods ranging from 3 weeks to 7 months.
RESULTS In total, 5 goats were studied . The optimal location for AVNI was located at the junction of the coronary sinus and inferior vena cava. Optimal AVNI was found at a stimulation frequency of 30Hz and pulse width of 180 μs in each animal. During the implant procedure “a safety window” appeared to be present. However, it became smaller after a longer period of AVNS. The acute effect of AVNI (averaged over the experiments) was a prolongation of the median R-R interval of 37 % (SD = 21%), which was not significantly different from the chronic effect at the end of the study (average = 32% (SD = 18%).
CONCLUSIONS Chronic intra-cardiac AV-node inhibition to reduce the ventricular rate during AF is feasible. Atrial pro-arrhythmic effects can be avoided by optimization of the stimulus parameters and location.