◼ atrioventricular node ◼ autonomic nervous system ◼ ECG ◼ ventricular rate Neural Control of Ventricular Rate in Ambulatory Dogs With Pacing - Induced Sustained Atrial Fibrillation

• • Randomized clinical trials have shown that in most patients with atrial fibrillation (AF), rate control is not inferior to rhythm control as a management strategy. However, the mechanisms of ventricular rate (VR) control during AF remain unclear. Commonly accepted mechanisms are that the complex local atrial wavefronts play an important role in modulating atrioventricular (AV) node conduction through irregularity and randomness of the atrial activity itself and through repetitive anterograde concealment and electrotonic modulation of the AV node conduction. In addition, it is also generally accepted that autonomic nervous system inputs, especially the vagal tone, are important in modulating AV node conduction. Based on studies using anesthetized animals, there are parallel yet functionally distinct inputs from right and left vagal nerves to AV node. Left vagal nerve stimulation has been proposed as a method to control VR during AF. In addition to vagal nerves, it is also known that the inferior vena cava–inferior atrial ganglionated plexus (IVC-IAGP; also known as the inferior right or right inferior ganglionated plexi [GP]) is important in modulating AV node conduction and that direct electric stimulation of this GP may slow VR during AF in human patients. However, none of these studies was performed in the ambulatory state with direct nerve recording. Therefore, the relative importance of right vagal nerve activity (RVNA), left vagal nerve activity (LVNA), and IVC-IAGP nerve activity (IVC-IAGPNA) in VR control during AF in ambulatory animals remains poorly understood in the ambulatory state. Furthermore, whether VR reduction is achieved by vagal nerve activity (VNA) or by IVC-IAGPNA remains unclear. We have developed methods to simultaneously record nerve activities (NAs) from the extrinsic nervous system and GPs in ambulatory dogs. The purpose of the present study is to use these techniques to simultaneously record RVNA, LVNA, and IVC-IAGPNA in dogs with pacing-induced sustained AF to test the hypothesis that IVC-IAGPNA is primarily responsible for VR control during AF in ambulatory dogs.