Neuronal Modulation of Atrial and Ventricular Electrical Properties

Abstract

Abstract As reviewed in Chapter 4, anatomically and functionally complex neuronal aggregates that are involved in coordinating regional cardiac function exist in intrathoracic extracardiac as well as intrinsic cardiac ganglia. It has been proposed that the intrinsic cardiac nervous system represents the final common pathway for the control of regional cardiac function. This system integrates afferent neuronal information arising from the heart to exert spatial and temporal control over cardiac efferent neurons regulating different cardiac regions. As such, it forms part of a hierarchy of intrathoracic and central neuronal feedback loops involved in regulating regional cardiac dynamics.6 In this scheme, neurons located in the various intrinsic cardiac ganglionated plexuses play a major role in beat­ to-beat regulation of regional cardiac function, a role that has traditionally been minimized to the benefit of local mechanical interactions (the Frank-Starling hypothesis). One outstanding issue in the field of neurocardiology concerns the patterns of efferent neuronal projections to various cardiac regions arising from the different ganglionated plexuses located in divergent atrial and ventricular regions. At present, this is a subject of considerable controversy. Some authors believe that neurons in the right atrial ganglionated plexus, for instance, subserve solely sinus nodal function whereas those in the inferior vena cavalinferior left ventricular ganglionated plexus exert predominant control over the atrioventricular node. In contrast, it has been our contention that the multiple neurons existing within a given ganglionated plexus modulate divergent car­ diac regions while displaying preferential control over regional cardiac function.