Anatomy of Intrinsic Cardiac Autonomic Nervous System
The human heart contains more than one and a half thousand autonomic ganglia (5) which cluster in anatomically well-defined areas known as GPs (6). While ablation of autonomic ganglionic plexi (GPs) causes permanent damage because neurons are amitotic and cannot be replaced, ablation of myocardial and endocardial efferent nerve fibers will only cause a transient effect due to the regeneration capability of nerve fibers. As such, from a clinical electrophysiologist’s perspective, understanding the difference between GPs and the pathway of innervation from autonomic ganglia to the heart is important to create a framework for ablation therapies so as to directly target neuromodulation of intrinsic cardiac ANS.
Based on Armour’s GP nomenclature the following atrial locations contain most GPs: (1)superior right atrial GP; (2) superior left atrial GP; (3) posterior right atrial GP; (4) posteromedial left atrial GP; (5) interatrial septal GP; and (6) posterolateral left atrial GP (6). The vein of Marshall may also be considered part of the intrinsic cardiac ANS because parasympathetic fibers from the vein of Marshall innervate surrounding left atrial structures and the coronary sinus (7). Figure 1 schematically illustrates distribution of major atrial GPs which are usually targeted during CNA based on 3D mapping.