The Anatomic Atrial Connections Between Sinus and A-V Node

Merideth, John; Titus, Jack L.

doi:10.1161/01.cir.37.4.566

Cited by 101 publications

(21 citation statements)

References 33 publications

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“…Rarely, these bypass fibers penetrated directly into the crest of the interventricular septum. Such bypass tracts, as a feature of the norm al A V node, have not been found by others (9,16,126). Because of the functional implications of the term bypass tract, namely that impulses from the atrium can be transmitted without delay to the beginning of the atrioventricular bundIe or the ventricular septum, it is useful to use a strict definition.…”

Section: Atrial Overlay Fibers and Bypass Tractsmentioning

confidence: 94%

Morphology and electrophysiology of the mammalian atrioventricular node

Meijler

Janse

1988

Physiological Reviews

203

146

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The AV node of those mammalian species in which it has been thoroughly investigated (rabbit, ferret, and humans) consists of various cell types: transitional cells, midnodal (or typical nodal cells), lower nodal cells, and cells of the AV bundle. There are at least two inputs to the AV node, a posterior one via the crista terminalis and an anterior one via the interatrial septum, where atrial fibers gradually merge with transitional cells. The role of a possible third input from the left atrium has not been investigated. Since the transition from atrial fibers to nodal fibers is gradual, it is very difficult to define the "beginning" of the AV node, and gross measurements of AV nodal length may be misleading. Histologically, the "end" of the AV node is equally difficult to define. At the site where macroscopically the AV node ends, at the point where the AV bundle penetrates into the membranous septum, typical nodal cells intermingle with His bundle cells. A conspicuous feature, found in all species studied, is the paucity of junctional complexes, most marked in the midnodal area. The functional counterpart of this is an increased coupling resistance between nodal cells. An electrophysiological classification of the AV nodal area, based on transmembrane action potential characteristics during various imposed atrial rhythms (rapid pacing, trains of premature impulses), into AN (including ANCO and ANL), N, and NH zones has been described by various authors for the rabbit heart. In those studies in which activation patterns, transmembrane potential characteristics, and histology have been compared, a good correlation has been found between AN and transitional cells, N cells and the area where transitional cells and cells of the beginning of the AV bundle merge with midnodal cells, and NH cells and cells of the AV bundle. Dead-end pathways correspond to the posterior extension of the bundle of lower nodal cells and to anterior overlay fibers. During propagation of a normal sinus beat, activation of the AN zone accounts for at least 25% of conduction time from atrium to His bundle, the small N zone being the main source of AV nodal delay. Cycle length-dependent conduction delay is localized in the N zone. Conduction block of premature atrial impulses can occur both in the N zone and in the AN zone, depending on the degree of prematurity. Several factors determining AV nodal conduction delay have been identified.(ABSTRACT TRUNCATED AT 400 WORDS)

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Section: Atrial Overlay Fibers and Bypass Tractsmentioning

confidence: 94%

Morphology and electrophysiology of the mammalian atrioventricular node

Meijler

Janse

1988

Physiological Reviews

203

146

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“…Successful experiments were made on hearts from 28 dogs of the following age ranges (7 per group): 1-7 days (newborn), 1-12 weeks (puppy), and two groups of adult dogs, [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] Circulation Research, Vol. XXIX, AuguU 1971 months, and over 2 years.…”

Section: Methodsmentioning

confidence: 99%

“…Meredith and Titus (10), on the other hand, summarized their results by stating that their study did not reveal any striking structural differences between cells composing "specific pathways and ordinary atrial cells," and commented that the question whether there are atrial conducting pathways is, in part, one of semantics. Functional evidence used to support the idea of specialized atrial tracts has been largely based on differences in the shape of intracellular action potentials (11)(12)(13) and in the sensitivity of cells to changes in external potassium (14).…”

mentioning

confidence: 99%

Excitation Sequences of the Atrial Septum and the AV Node in Isolated Hearts of the Dog and Rabbit

Spach

Lieberman

Scott

et al. 1971

Circulation Research

124

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The spread of excitation wave fronts over the atrial septum of puppies, adult dogs, and rabbits was studied in vitro by extracellular measurements with a 50/x-diameter electrode. Wave front spread through the AV node of puppies and rabbits was determined, and the functional location of the junctional region between atrial muscle and the AV node was evaluated during antegrade atrial and retrograde His bundle pacing. For dogs of all ages, the pattern of spread over the septum was greatly affected by the location of the pacemaker site simulating a high or low sinus node position. For all sinus pacing positions, wave fronts spread over the crista terminalis to form a posterior input to the AV node, while the anterior septal wave fronts formed another input. No functional evidence could be found for narrow, specialized intemodal tracts of fixed location. Rather, wave fronts spread over broad areas creating patterns of simultaneous, multiple wave fronts which corresponded in extent to the gross anatomical landmarks of the septum. Only in this fashion were the findings consistent with the idea of three general routes of intemodal conduction in the dog and two general routes in the rabbit. The position of the functional boundary between atrium and AV node could be accounted for only by overlapping of the two tissues of this region; the boundary shifted between antegrade and retrograde conduction. Antegrade wave fronts within the AV node accelerated from the superior border of the node to the exit at the His bundle; retrograde excitation wave fronts from the His bundle decelerated through the AV node. The amplitude of the atrial wave forms as well as the status of die inputs from the posterior and anterior regions of the atrial septum were found to be important factors in AV node conduction. KEY WORDSatrial septal excitation maps intemodal tracts extracellular-intracellular potentials atrium-AV node junction AV node excitation maps retrograde AV node activation• Whether or not one includes propagation through the atrium as part of atrioventricular (AV) transmission, one must know the sequence of activation of the atrial septum to understand AV transmission. The direction of atrial wave fronts as they approach the AV node have been shown to modify transmissionFrom the

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“…1965;H udson, 1967;T ruex et a i, 1967;Verhaeghe and Van der Hauswaert, 1967;Merideth andTrrus, 1968: H romada andVoboril, 1970;Bojsf.n-M oller and T ranum-Jensen, 1972]. When searching for sources in the literature dealing with the cardiac conduction system, the Received: September I, 1975. authors only found one single paper dealing with the lymph of this tissue, actually of the bundle of His [Curran, 1909]: here, this author describes the special perilymphatic space surrounding the atrio-ventricular bundle.…”

Section: Introductionmentioning

confidence: 99%

Lymph drainage of sinu-atrial node in man and dog

Eliška¹,

Elišková²

1976

Cells Tissues Organs

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The lymphatic vessels of the sinu-atrial (SA) node were investigated after injection of Indian ink plus gelatine in 62 canine and 31 human hearts, the latter of subjects aged between 21 and 80. Lymph was found to be chiefly drained from the SA node of the dog by a vessel which collected lymph near the left margin of the SA node and ran between the superior vena cava and the right circumference of the aorta into the left cardiac lymph collector and through it into the left cardiac node. Approximately in two thirds of cases this main lymph drainage was supplemented by smaller lymphatic branches running into the right tracheo-bronchial nodes. In man, the main route of lymph drainage from the SA node is represented by one or two vessels which run to the right and upwards along the superior vena cava into the inferior tracheo-bronchial nodes (of the bifurcation), lying near the right bronchus. Little branches draining lymph into the cardiac collector are found rarely. It has become evident from histological sections that the lymphatic vessels run between the cells of the conduction system and the collagenous fibres of connective tissue and are not numerous.

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The Anatomic Atrial Connections Between Sinus and A-V Node

Cited by 101 publications

References 33 publications

Morphology and electrophysiology of the mammalian atrioventricular node

Morphology and electrophysiology of the mammalian atrioventricular node

Excitation Sequences of the Atrial Septum and the AV Node in Isolated Hearts of the Dog and Rabbit

Lymph drainage of sinu-atrial node in man and dog

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