Selective AV nodal vagal stimulation improves hemodynamics during acute atrial fibrillation in dogs

Abstract

Although the atrioventricular node (AVN) plays a vital role in blocking many of the atrial impulses from reaching the ventricles during atrial fibrillation (AF), a rapid irregular ventricular rate nevertheless persists. The goals of the present study were to explore the feasibility of novel epicardial selective vagal nerve stimulation for slowing of the ventricular rate during AF and to characterize the hemodynamic benefits in vivo. Electrophysiological-echocardiographic experiments were performed on 11 anesthetized open-chest dogs. Hemodynamic measurements were performed during three distinct periods: 1) sinus rate, 2) AF, and 3) AF with vagal nerve stimulation. AF was associated with significant deterioration of all measured parameters (P < 0.025). The vagal nerve stimulation produced slowing of the ventricular rate, significant reversal of the pressure and contractile indexes (P < 0.025), and a sharp reduction in one-half of the abortive ventricular contractions. The present study provides comprehensive evidence that slowing of the ventricular rate during AF by selective ganglionic stimulation of the vagal nerves that innervate the AVN successfully improved the hemodynamic responses.

Optimal ventricular rate slowing during atrial fibrillation by feedback AV nodal-selective vagal stimulation

“…It is well established that stimulation of parasympathetic nerves, which selectively innervate the AVN, can slow AV conduction (2,6,12,13,21,(28)(29)(30). In our recent in vitro study, we found that vagally induced slowing of the VR during AF is feasible by using postganglionic endocardial nerve stimulation (23), whereas similar effects were also obtained by utilizing epicardial (44) or endocardial (36)(37)(38)(39) nerve stimulation in vivo. This approach is nondestructive and associated with maintenance of physiological anterograde propagation of the cardiac beat.…”

“…Custom-made Ag-AgCl quadripolar plate electrodes were sutured to the high right atrium and right ventricular apex for bipolar pacing and recording. Similar bipolar plate electrodes were also sutured to two epicardial fat pads that contain parasympathetic neural pathways selectively innervating the sinus node (SN) and the AVN, the right pulmonary vein-atrial junction fat pad, and the inferior vena cava-left atrium fat pad, respectively (44). The ascending aorta was isolated, and a flow probe was placed around it and connected to a flowmeter (16A/20A, HT 207, Transonic System; Ithaca, NY) to display and measure aortic flow (AoF).…”

Sensing and stimulation of the vagus nerve for artificial cardiac control

“…Also, the pig and human vagus nerve diameter are larger than that of a rat, which may complicate recording. Spectral analysis of the vagus nerve was also analyzed by Rozman and colleagues, who made recordings from the vagus nerve with an extraneural segmented cuff in dogs [30]. Power spectra were obtained that were found to provide organ-specific information on selected segments.…”

“…This network consists of the interconnected ganglionated plexus on the epicardium of the heart. This complex neural network on the heart, also called 'the little brain on the heart' integrates afferent and efferent as well as parasympathetic and sympathetic activity as a final relay station, and is thought to be important in the coordinated neural control of the heart [23,30]. The heart is not the only organ with an intrinsic nervous system.…”

“…For example, selective cardiac effects can be achieved by stimulating discrete fat pads. Different fat pads can be stimulated to selectively slow sinus rate [30], block AV node conduction [19,[31][32][33], or influence the ventricles [31,33]. It needs to be studied whether fat pad stimulation is advantageous over cervical vagus nerve stimulation for cardiac diseased states, and how this can be achieved in a minimally invasive way.…”