The spatial distribution and relative abundance of gap-junctional connexin40 and connexin43 correlate to functional properties of components of the cardiac atrioventricular conduction system

1993 ◽  
Vol 105 (4) ◽  
pp. 985-991 ◽  
Author(s):  
R.G. Gourdie ◽  
N.J. Severs ◽  
C.R. Green ◽  
S. Rothery ◽  
P. Germroth ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Relative Abundance ◽  
Atrioventricular Node ◽  
Conduction System ◽  
Atrioventricular Conduction ◽  
Purkinje Fibre ◽  
Purkinje Fibres ◽  
Atrioventricular Bundle ◽  
Junctional Protein ◽  
Gap Junctional

Electrical coupling between heart muscle cells is mediated by specialised regions of sarcolemmal interaction termed gap junctions. In previous work, we have demonstrated that connexin42, a recently identified gap-junctional protein, is present in the specialised conduction tissues of the avian heart. In the present study, the spatial distribution of the mammalian homologue of this protein, connexin40, was examined using immunofluorescence, confocal scanning laser microscopy and quantitative digital image analysis in order to determine whether a parallel distribution occurs in rat. Connexin40 was detected by immunofluorescence in all main components of the atrioventricular conduction system including the atrioventricular node, atrioventricular bundle, and Purkinje fibres. Quantitation revealed that levels of connexin40 immunofluorescence increased along the axis of atrioventricular conduction, rising over 10-fold between atrioventricular node and atrioventricular bundle and a further 10-fold between atrioventricular bundle and Purkinje fibres. Connexin40 and connexin43, the principal gap-junctional protein of the mammalian heart, were co-localised within atrioventricular nodal tissues and Purkinje fibres. By applying a novel photobleach/double-labelling protocol, it was demonstrated that connexin40 and connexin43 are co-localised in precisely the same Purkinje fibre myocytes. A model, integrating data on the spatial distribution and relative abundance of connexin40 and connexin43 in the heart, proposes how myocyte-type-specific patterns of connexin isform expression account for the electrical continuity of cardiac atrioventricular conduction.

scholarly journals Specialized impulse conduction pathway in the alligator heart

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Bjarke Jensen ◽  
Bastiaan J Boukens ◽  
Dane A Crossley ◽  
Justin Conner ◽  
Rajiv A Mohan ◽  
...  
Keyword(s):  
Conduction System ◽  
Atrioventricular Conduction ◽  
Alligator Mississippiensis ◽  
Ventricular Septum ◽  
Heart Rates ◽  
Conduction Pathway ◽  
Atrioventricular Bundle ◽  
Rapid Activation ◽  
Ventricular Conduction ◽  
Purkinje Network

Mammals and birds have a specialized cardiac atrioventricular conduction system enabling rapid activation of both ventricles. This system may have evolved together with high heart rates to support their endothermic state (warm-bloodedness) and is seemingly lacking in ectothermic vertebrates from which first mammals then birds independently evolved. Here, we studied the conduction system in crocodiles (Alligator mississippiensis), the only ectothermic vertebrates with a full ventricular septum. We identified homologues of mammalian conduction system markers (Tbx3-Tbx5, Scn5a, Gja5, Nppa-Nppb) and show the presence of a functional atrioventricular bundle. The ventricular Purkinje network, however, was absent and slow ventricular conduction relied on trabecular myocardium, as it does in other ectothermic vertebrates. We propose the evolution of the atrioventricular bundle followed full ventricular septum formation prior to the development of high heart rates and endothermy. In contrast, the evolution of the ventricular Purkinje network is strongly associated with high heart rates and endothermy.

Differentiation and innervation of the atrioventricular bundle and ventricular Purkinje system in sheep heart

Development ◽  
1987 ◽  
Vol 100 (4) ◽  
pp. 641-651
Author(s):  
E. Canale ◽  
J.J. Smolich ◽  
G.R. Campbell
Keyword(s):  
Intermediate Filaments ◽  
Morphological Changes ◽  
Atrioventricular Node ◽  
Ventricular Wall ◽  
Nerve Fibres ◽  
Fetal Sheep ◽  
Purkinje Fibres ◽  
Developmental Mechanism ◽  
Purkinje System ◽  
Atrioventricular Bundle

The development of the atrioventricular bundle (AVB) and ventricular Purkinje system and their innervation have been studied in fetal sheep from 27 to 140 days gestation (term is 147 days). The AVB initially consisted of a primordium, which lacked innervation and was composed of small, relatively undifferentiated myocytes. Differentiation of Purkinje-like cells within the AVB began near its distal end and extended towards the atrioventricular node (AVN). Differentiation of the ventricular Purkinje system extended distally from the region of bifurcation of the AVB from cells that were indistinguishable from the working myocardium and continuous with the AVB primordium. Differentiation of Purkinje-like AVB cells was complete by 46 days gestation but Purkinje fibres were still differentiating within the ventricular wall at 60 days gestation. The main morphological changes included a large increase in cell size and organization into strands, development of characteristic glycogen-filled regions containing many intermediate filaments and early development of myofibrillar M lines compared to the working myocardium. The differentiation of AVB cells and the ventricular Purkinje system preceded their innervation. The AVB became innervated earlier than ventricular Purkinje fibres, intimate contacts between proximal AVB cells and nerve axons being present at 60 days gestation. Nerve fibres were present in the septomarginal band at this time, however, en passant associations with ventricular Purkinje fibres were rarely observed until 140 days gestation and intimate contacts were not present at any stage. Although the AVB and ventricular Purkinje system of adult sheep are composed of morphologically similar cells, the present study demonstrates that they differ in origin and their mode of differentiation as well as timing and intimacy of innervation. Innervation is not part of the developmental mechanism leading to the differentiation of Purkinje fibres. No primordium of the ventricular Purkinje system could be identified, suggesting that the mechanism of differentiation of ventricular Purkinje fibres involves recruitment from early working myocardium.

ANATOMY OF THE ATRIOVENTRICULAR NODE AND ATRIOVENTRICULAR CONDUCTION SYSTEM

2003 ◽  
Vol 13 (12) ◽  
pp. 3665-3674 ◽  
Author(s):  
SIEW YEN HO ◽  
KAREN P. McCARTHY ◽  
ANEEL ANSARI ◽  
PENNY S. THOMAS ◽  
DAMIAN SÁNCHEZ-QUINTANA
Keyword(s):  
Cardiac Arrhythmias ◽  
Right Atrium ◽  
Atrioventricular Node ◽  
Ventricular Myocardium ◽  
Conduction System ◽  
Atrioventricular Conduction ◽  
Laboratory Animals ◽  
Atrial Myocardium ◽  
The Right

The anatomy of the atrioventricular conduction system was first described nearly a hundred years ago. Since then, it has been an occasional subject of controversy mainly through a lack of adherence to the original definitions based on histology. The gross landmarks for locating the atrial component of the conduction system are found in the right atrium. The components and structure of the system in human are comparable to that found in commonly used laboratory animals. The conduction system is composed of specialized myocytes. Its atrial component, the atrioventricular node, is in contact with atrial myocardium. Having penetrated the atrioventricular insulating plane, the major ventricular bundles are encased in fibrous sheaths that separate the specialized myocytes from the ordinary myocardium. Only at the distal ramifications of the bundle branches do the fibrous sheaths disappear, allowing continuity with ventricular myocardium. Being the only muscular pathway connecting atrial with ventricular myocardium, knowledge of its structure can help in developing potential therapies for some forms of cardiac arrhythmias.

Surgical anatomy of the atrioventricular septum and atrioventricular septal defects

1991 ◽  
Vol 1 (4) ◽  
pp. 306-314
Author(s):  
G. William Henry ◽  
Benson R. Wilcox
Keyword(s):  
Atrioventricular Node ◽  
Surgical Anatomy ◽  
Conduction System ◽  
Atrioventricular Conduction ◽  
Atrioventricular Valve ◽  
Atrioventricular Valves ◽  
Atrioventricular Septal Defects ◽  
Septal Defects

SummaryDefects of the atrioventricular septum impose changes in the septal architecture, atrioventricular valves, and conduction system that must be well understood for optimal repair. The atrioventricular node and bundles are shifted to more posterior and inferior positions that can be anticipated by the surgeon so as to maintain the integrity of atrioventricular conduction. The atrioventricular valve is a five leaflet structure that possesses a common orifice or separate orifices depending on characteristics of the superior and inferior bridging leaflets. These features are demonstrated by intraoperative photographs viewed from the surgeon's position.

scholarly journals Hypertrophic cardiomyopathy with paroxysmal atrial fibrillation misdiagnosed as WPW syndrome

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Sang-Hoon Seol ◽  
Ki-Hun Kim ◽  
Jino Park ◽  
Yeo-Jeong Song ◽  
Dong-Kie Kim ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Hypertrophic Cardiomyopathy ◽  
Paroxysmal Atrial Fibrillation ◽  
Conduction System ◽  
Atrioventricular Conduction ◽  
Wpw Syndrome ◽  
Bypass Tract ◽  
Hypertrophied Myocardium

AbstractHypertrophic cardiomyopathy (HCM) is associated with an increased incidence of Wolff–Parkinson–White (WPW) syndrome and atrial fibrillation. However, a delta-like wide QRS can be observed in the hypertrophied myocardium. When considering the rarity of the paraseptal bypass tract (BT), the normal QRS axis suggests a higher possibility of HCM origin. Otherwise, there is no known electrocardiographic clue indicating a wide QRS differentiation between HCM and WPW syndrome. Moreover, the atriofascicular, nodofascicular/ventricular or fasciculoventricular BT should be differentiated. In this case, atrioventricular conduction system incidental injury revealed a wide QRS origin from the HCM, but this method should be avoided except in some selected cases.

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