A morphologic study of the cardiac conduction system in ungulates, dog, and man

Glomset, Daniel J.; Glomset, Anna T.A.

doi:10.1016/s0002-8703(40)90873-0

Cited by 102 publications

(24 citation statements)

References 8 publications

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“…As for the atrial contraction, therefore, I support the opinion mentioned by TRUEX and SMYTHE (1965). GLOMSET and GLOMSET (1940), GLOMSET and BIRGE (1945), in their studies on human and dog heart, considered that specialized muscle fibers do not exsist in the both atria and ventricles, and that muscle fibers in the so called conduction system only correspond to one type of ordinary heart muscle. Based on this opinion, they concluded that the impulse spread through the intracardiac nervous system, and not through the conduction system.…”

Section: Discussionsupporting

confidence: 60%

“…MARCHAND (1885), ASCHOFF and NAGAYO (1908) reported that much glycogen is present in the conduction system of the heart. It has become clear that glycogen content and its distribution in the specialized tissue varies according to species of animal, age, general condition of the animal and part in the conduction system (MONCKEBERG 1924, NOLL and BECKER 1936, GLOMSET and GLOMSET 1940, COPEN-HAVER and TRUEX 1952. On the other hand, the precise distribution of glycogen in each part of conduction system of one species has not been studied.…”

Section: Discussionmentioning

confidence: 99%

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Morphological and Histochemical Studies on the Cardiac Conduction System of the Dog

Hara

1967

Arch. Histol. Jap., Arch. Histol. Jpn

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Section: Discussionsupporting

confidence: 60%

Section: Discussionmentioning

confidence: 99%

Morphological and Histochemical Studies on the Cardiac Conduction System of the Dog

Hara

1967

Arch. Histol. Jap., Arch. Histol. Jpn

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“…This is consistent with the estimations of critical size of excitation as mentioned above. All estimates are significantly larger than the diameter of terminal Purkinje fibers which can be less than 100 pm [39]. Several factors may be taken into account to explain this discrepancy.…”

Section: Estimation Of Critical Strand Width In Ventricular Tissue Anmentioning

confidence: 81%

Block of impulse propagation at an abrupt tissue expansion: evaluation of the critical strand diameter in 2- and 3-dimensional computer models

FAST¹

1995

Cardiovascular Research

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. ___ .-_---_----Objective: Unidirectional conduction block in the heart can occur at a site where the impulse is transmitted from a small to a large tissue volume. The aim of this study was to evaluate the occurrence of conduction block in a 2-dimensional and 3-dimensional computer model of cardiac tissue consisting of a narrow strand abruptly emerging into a large area. In this structure, the strand diameter critical for the occurrence of block, h,, was evaluated as a function of changes in the active and passive electrical properties of both the strand and the large medium. M&hods: The effects of changes in the following parameters on h, were analysed: (I 1 maximum sodium conductance (gNa,,, 1, (21 longitudinal (R,) and transverse (R,) intracellular resistivities, and (3) inhomogeneities in gNa,,,, and R, and R," between the strand and the large area. Three ionic models for cardiac excitation described by Beeler-Reuter, Ebihara-Johnson, andLuo-Rudy ionic current kinetics were compared. Results: In the 2-dimensional simulations, h, was 175 pm in Ebihara-Johnson and Beeler-Reuter models and 200 pm in the Luo-Rudy model. At the critical strand diameter, the site of conduction block was located beyond the transition, i.e. a small circular area was activated in the large medium, whereas with narrower strands conduction block occurred within the strands. The decrease of gNa,,, resulted in a large increase of h,. This increase was mainly due to the change of d%7l,x in the large area, while h, was almost independent of giva,,, in the strand. Changing R, had no effect on h,, whereas the increase of R, decreased h, and reversed conduction block. Inhomogeneous changes of R, and R, in the strand versus the large medium had opposite effects on h,. When the resistivities of the strand alone were increased, h, also increased. In contrast, the increase of the resistivities in the large area reduced h,. In the 3-dimensional model, h, was 2.7 times larger than the corresponding Sdimensional values at the various levels of gNa,,, and resistivity. Conclusions: (1) At physiological values for active and passive electrical properties, h, in the 2D simulations is close to 200 pm in all three ionic models. In the 3-dimensional simulations, I?, is 2.7 larger than in the 2-dimensional models. (2) The excitable properties of the large area but not of the strand modify h,.. The decrease of intercellular coupling in the large medium facilitates impulse conduction and reduces h,., while the same change in the strand increases h,.. (3) Occurrence of conduction block at an abrupt geometrical transition can be explained by both the impedance mismatch at the transition site and the critical curvature beyond the transition.

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“…(1) the presence of an accessory conducting pathway which bypasses the normal AV node (7,8) or (2) an AV node which does not have the long refractory, slow conducting characteristics found in most adult mammalian AV nodes. The present study was undertaken to distinguish which mechanism operates in the young goat heart.…”

mentioning

confidence: 99%

The differences in atrioventricular conduction of premature beats in young and adult goats.

Gough¹,

Moore²

1975

Circulation Research

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Atrioventricular (AV) conduction was studied in anesthetized, open-chest, 1-35-day-old goats. Atrial, bundle of His, and ventricular bipolar electrograms were recorded, and the functional refractory periods of the AV conduction system and the ventricles were determined. Supraventricular premature excitation invaded the ventricles during their vulnerable period. This AV conduction property is different from that of the adult goat heart; thus, the existence of a lateral accessory bypass tract was investigated. Electrocardiographic leads I, aVF, and V, o revealed no delta waves indicative of ventricular preexcitation. Bundle of His electrograms showed that: (1) bundle of His excitation always preceded the onset of ventricular depolarization, (2) no shortening occurred in the bundle of His to ventricular activation time following early atrial premature beats, and (3) the functional refractory period of the AV node was less than that of the ventricle. The ventricular epicardial excitation sequence indicated no involvement of a lateral bypass tract in the AV conduction of basic or premature beats. Interruption of the bundle of His caused complete AV block. Therefore, no functional lateral accessory bypass tracts are present in the young goat heart, and the AV node and the ventricular specialized conduction system of the young goat are capable of conducting premature atrial excitation to the ventricles within ±10 msec of the expiration of the ventricular functional refractory period.• Atrioventricular (AV) conduction of premature beats has been studied in several different mammalian species (1-6); however, only two reports deal with AV conduction of premature beats in young mammalian hearts (5, 6). Preston et al. (6) have reported that young ventricles are prematurely excited at an interval equal to their functional refractory period by premature atrial beats. This capacity of the AV transmission system for such rapid conduction of premature atrial beats permits premature atrial excitation to evoke ventricular fibrillation. In normal adult dog or human hearts, the AV node serves as a filter to protect the ventricles from early premature atrial beats (4, 6).Two basic mechanisms could explain this AV conduction property of young mammalian hearts: 48(1) the presence of an accessory conducting pathway which bypasses the normal AV node (7, 8) or (2) an AV node which does not have the long refractory, slow conducting characteristics found in most adult mammalian AV nodes. The present study was undertaken to distinguish which mechanism operates in the young goat heart. Four techniques were utilized: (1) electrocardiography, (2) intracardiac recordings from the bundle of His, (3) mapping of the sequence of ventricular epicardial excitation, and (4) surgical interruption of the bundle of His. The results showed that the AV node of the young goat has a shorter functional refractory period than does the adult AV node; we found no electrophysiological evidence to suggest the existence of bypass tracts. MethodsThirty-sev...

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A morphologic study of the cardiac conduction system in ungulates, dog, and man

Cited by 102 publications

References 8 publications

Morphological and Histochemical Studies on the Cardiac Conduction System of the Dog

Morphological and Histochemical Studies on the Cardiac Conduction System of the Dog

Block of impulse propagation at an abrupt tissue expansion: evaluation of the critical strand diameter in 2- and 3-dimensional computer models

The differences in atrioventricular conduction of premature beats in young and adult goats.

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