REGIONAL DISTRIBUTION OF ATRIAL ELECTRICAL CHANGES INDUCED BY STIMULATION OF EXTRACARDIAC AND INTRACARDIAC NEURAL ELEMENTS

Autonomic nerves and intrinsic cardiac neural elements are known to in fluence the electrophysiologic and dynamic properties of the heart, Th is study describes the regional distribution in the canine atria of el ectrophysiologic effects induced by stimulation of the right and left cervical vagosympathetic complexes, the right atrial ganglionated plex us, and the right and left stellate ganglia. Local atrial effects were determined from changes in QRST area of unipolar electrograms recorde d from multiple sites with plaque electrodes sewn onto the atria in 16 anesthetized dogs. Results: (1) Although being very consistent in any given preparation, atrial changes varied between animals when similar neural structures were stimulated. (2) Among the common features iden tified between preparations, consistent effects were induced by neural stimulation in the region of the sinus node, indicating that this atr ial region is the most richly innervated. (3) All other regions of the atria could be affected by stimulation of either right-sided or left- sided efferent nerves. (4) Responses to right atrial ganglionated plex us stimulation after atropine administration indicated that the corres ponding fat pad contains both sympathetic and parasympathetic neural e lements. Conclusion: This study demonstrates that there is considerabl e overlapping of atrial innervation affecting all regions of the atria , as well as the sinus node region.