Functional anatomy of the canine mediastinal cardiac nerves located at the base of the heart

Abstract

The major canine cardiopulmonary nerves which arise from the middle cervical and stellate ganglia and the vagi course toward the heart in the dorsal mediastinum where they form, at the base of the heart dorsal to the pulmonary artery and aorta, the dorsal mediastinal cardiac nerves. In addition, the left caudal pole and interganglionic nerves project onto the left lateral side of the heart as the left lateral cardiac nerve. These nerves contain afferent and (or) efferent axons which, upon stimulation, modify specific cardiac regions and (or) systemic pressure. In addition, with the exception of the left lateral cardiac nerve, stimulation of each of these nerves produces compound action potentials in the cranial ends of the majority of the major cardiopulmonary nerves demonstrating that axons in each dorsal mediastinal cardiac nerve interconnect with axons in the majority of the cardiopulmonary nerves. Axons in the left lateral cardiac nerve connect primarily with axons in the left caudal pole and left interganglionic nerves. The dorsal mediastinal nerves project distally onto the heart as coronary nerves accompanying the right or left coronary arteries. These innervated the ventricular myocardium which is supplied by their respective vessels. The left lateral cardiac nerve projects directly onto the lateral epicardium of the left ventricle. The dorsal mediastinal and left lateral cardiac nerves are the major sympathetic cardiac nerves. Thus, the cardiac nerves located in the mediastinum at the base of the heart are not simple extensions of cardiopulmonary nerves, but rather have a unique anatomy and function of their own.

Augmentation of Left Ventricular Contractility by Cardiac Sympathetic Neural Stimulation

“…The left lateral cardiac nerve courses adjacent to the left atrial appendage and anterior to the left pulmonary veins onto the left lateral myocardium. 10 In dogs, it is the offspring of the ventrolateral nerve. 7 Besides these 3 major nerves, small cardiac nerves arise from various cardiopulmonary plexus and the thoracic vagal nerves that innervate overlapping regions of the LV 11,19,20 or right ventricle.…”

“…[7][8][9] Previous anatomic studies have shown that sympathetic fibers also cross the coronary sinus (CS). 10,11 To identify these fibers, a deflectable 8-mm-tip multielectrode catheter (Cordis Corp) was introduced inside the CS via the left jugular vein and connected to an external stimulator (Grass-S-88 stimulator, Astro-Med Inc, West Warwick, RI). To avoid inadvertent electric stimulation of the atria or ventricles, high-frequency stimulation (HFS) trains within the myocardial refractory periods (train duration, 50 ms; frequency, 200 Hz; 37.5 V; 2-ms pulse duration) were coupled to the pacing stimulus during atrial (nϭ20) or ventricular (nϭ8) pacing at a delay of 20 ms.…”

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

“…7,8 These nerves are known to provide neural inputs to the intrinsic cardiac ganglionated plexuses and to cardiac muscle, and carry afferent information to the various levels of the cardiac neuronal hierarchy. 23 The fact that all tachyarrhythmia responses to mediastinal nerve stimulation were completely abolished by atropine is consistent with the view that cholinergic efferent neurons play a predominant role in neurally mediated atrial tachyarrhythmia formation in normal canines, 19,24 -29 although adrenergic modulatory influences can also be demonstrated.…”

“…7,8 Such nerves, which can be identified in humans 9 -11 as well as in canines, 7,8 represent a major route of autonomic neural input to the intrinsic cardiac nervous system, together with nerves coursing along the superior vena cava and the PVs. 12,13 Using multielectrode atrial mapping in the canine heart-a standard model to study the cardiac nervous system that bears good correspondence to human 14,15 -we show that the initial beats of ATs induced when electric stimuli are applied to dorsal mediastinal nerves occur most frequently without any prior neurally induced sinus rate modification and originate from several distinct left atrial locations that include the PV region.…”

Gross anatomical study of the sympathetic cardiac nerves in the house musk shrew (Suncus murinus)

“…In addition, many comparative anatomical studies have been carried out on autonomic cardiac innervation in various vertebrate species, such as the calf (Shaner, 1930), rat (Gómez, 1958;Burkholder et al, 1992;Batulevičius et al, 2004), chick (Kuratani and Tanaka, 1990;Verberne et al, 1998Verberne et al, , 1999, musk shrew (Tanaka et al, 1998), guinea pig (Batulevičius et al, 2005), dog (Randall and Rohse, 1956;Itoh, 1960;Randall et al, 1963Randall et al, , 1968Randall et al, , 1972Randall et al, , 1989Szentivanyi et al, 1967;Randall, 1975, 1985;Norris and Randall, 1977;Rinkema et al, 1982;Armour, 1984, 1989;Brandys et al, 1986;Ardell et al, 1988;Armour, 1988;Gagliardi et al, 1988;Brugnaro et al, 2003), cat (Phillips et al, 1986), and primates (Riegele, 1926;Randall et al, 1971;Billman et al, 1989;Kawashima et al, 2001. Especially, Randall (1975, 1985) contributed to our knowledge of cardiac function using methods such as retrograde tracing and electrophysiology in dogs.…”