The ligament of Marshall as a parasympathetic conduit

Abstract

The objective of the study was to investigate the morphology, distribution, and electrophysiological profile of the autonomic fibers that innervate the ligament of Marshall (LOM). Gross anatomical dissections were performed in 10 dogs. Sections of the left vagus nerve, left stellate ganglion, and the LOM were immunostained to identify adrenergic and cholinergic nerves. Hearts were also stained for acetylcholinesterase to identify epicardial cholinergic nerves. In vivo electrophysiological studies were performed in another 10 dogs before and after LOM ablation. The anatomical examination revealed that the LOM is innervated by a branch of the left vagus. Immunohistochemistry confirmed that these nerve bundles are predominantly cholinergic (cholinergic-to-adrenergic ratio of 12.6 +/- 3.9:1). Cholinergic nerves originating in the LOM were found to innervate surrounding left atrial structures, including the pulmonary veins, left atrial appendage, coronary sinus, and posterior left atrial fat pad. Ablation of the LOM significantly attenuated effective refractory period shortening at distant sites, such as pulmonary veins and left atrial appendage, in response to vagal stimulation (vagal-induced ERP decrease in the left atrium: baseline vs. postablation = 17 vs. 4%; P = 0.0056). In conclusion, the LOM contains a predominance of cholinergic nerve fibers. Cholinergic fibers arising from the LOM innervate surrounding structures and contribute to the electrophysiological profile of the left atrium. These findings may provide a basis for the role of the LOM in the genesis and maintenance of atrial fibrillation.

Isolation of Canine Coronary Sinus Musculature From the Atria by Radiofrequency Catheter Ablation Prevents Induction of Atrial Fibrillation

“…Although this model of isolated tissue was separated from the central nervous system, acetylcholine release from local ganglia could still facilitate microreentry during AF. Epicardial RFCA to the CS-atrial junction or VOM would modify autonomic ganglia 25 as well as disconnect the macroand microreentrant circuits to terminate AF/AF.…”

Atrial Tachyarrhythmias and Repolarization Changes Induced by Discrete Activation of Dorsal Mediastinal Cardiac Nerves in Canines

“…37,38 When the early tachyarrhythmias beats originated from (1) the posterolateral LA wall next to the left PVs or (2) Bachmann bundle insertion into the superior RA wall, repolarization changes were concentrated in the atrial regions in which the tachyarrhythmia sites of origin were identified. The tachyarrhythmia sites of origin identified in the posterolateral LA wall (most frequently associated with left dorsal mediastinal nerve stimulation) were adjacent to the ligament of Marshall (which includes predominantly cholinergic neural elements in the canine heart 39 as well as to the LA and dorsal atrial ganglionated plexuses. Likewise, the tachyarrhythmia sites of origin identified in Bachmann bundle insertion into the superior RA (all associated with right dorsal mediastinal nerve stimulation) lay next to the superior extension of the RA ganglionated plexus.…”

Electrophysiological Features of Atrial Tachyarrhythmias After the Creation of a Left Atrial Roof Line During Catheter Ablation of Atrial Fibrillation

“…[20][21][22] The structural and functional characteristics of these regions, including the narrow and thick musculature, complex myofibril arrangement, and proximity to the autonomic ganglia and the ligament of Marshall may support the formation of a slow conduction obstacle of reentry due to the nontransmurality of the AF ablation lesions. 23,24) Study limitations : We did not use a 3D electroanatomical mapping system to evaluate the circuit of the induced ATs, or to confirm the block line along LARL. Therefore, there were some limitations in this study regarding assessment of the course of induced ATs.…”