A morphological study of the left bundle branch in the normal human heart

To clarify the distribution pattern of the left bundle branch (LBB) in the human heart, the AV conduction system was studied in 13 autopsied hearts obtained from subjects aged 50 to 80 years. Vertical serial sections (7 micron) of the bundle of His and LBB were prepared and every 20th section was stained alternately with hematoxylin-eosin (HE) or by the elastica van Gieson (EVG) method and examined by light microscopy. Reconstruction was performed using a two-dimensional system in order to histologically differentiate the bundle cells from Purkinje cells. The LBB bifurcated into the anterior and posterior radiations and the cells in the septal portion were almost all Purkinje cells except in two cases showing a septal branch between the two radiations. The LBB usually branched widely from the bundle of His. An extremely anterior fascicle of the LBB was found in all cases. The distribution of the LBB at the top of the ventricular septum was divided into network and continuous types. Purkinje cells were present on both the atrial and apical sides of the two main radiations. It was suggested that these findings resulted from the fact that we morphologically differentiated the bundle cells from Purkinje cells by light microscopy.     

A histopathological study of age-related changes of the left bundle branch in the human heart.

To study age-related changes in the left bundle branch (LBB), 32 autopsied hearts were examined histopathologically using serial sections according to the method of Lev. Each division of LBB was carefully studied, i.e., the anterior and posterior radiations and the proximal, middle, and distal portions of radiations. An increase of fibrosis and fatty infiltration were observed in the LBB with aging. There was a tendency for fibrosis to be more prominent in the proximal LBB at the site of transition from bundle branch cells to Purkinje cells.     

A Histopathological Study of Age-related Changes of the Left Bundle Branch in the Human Heart

To study age-related changes in the left bundle branch (LBB), 32 autopsied hearts were examined histopathologically using serial sections according to the method of Lev. Each division of LBB was carefully studied, i.e., the anterior and posterior radiations and the proximal, middle, and distal portions of radiations. An increase of fibrosis and fatty infiltration were observed in the LBB with aging. There was a tendency for fibrosis to be more prominent in the proximal LBB at the site of transition from bundle branch cells to Purkinje cells. Acta Pathol Jpn 41: 730-736, 1991.     

Cardiac conduction system in the chicken: Gross anatomy plus light and electron microscopy

Twenty-three chicken hearts were used to study the cardiac conduction system by light and electron microscopy. In addition to a sinus node, atrioventricular node (AVN), His bundle, left and right bundle branches (LBB, RBB), the chicken also has an AV Purkinje ring and a special middle bundle branch (MBB). The sinus node lies near the base of the lower portion of the right sinoatrial valve. The AV node is just above the tricuspid valve and anterior to the coronary sinus. The His bundle descends from the anterior and inferior margin of the AV node into the interventricular septum, then dividing into right, left and middle branches some distance below the septal crest. The middle bundle branch turns posteriorly toward the root of the aorta. The AV Purkinje ring originates from the proximal AV node and then encircles the right AV orifice, joining the MBB to form a figure-of-eight loop. The chicken conduction system contains four types of myocytes: (1) The P cell is small and rounded, with a relatively large nucleus and sparse myofibrils. (2) The transitional cell is slender and full of myofibrils. (3) The Purkinje-like cell resembles the typical Purkinje cell, but is smaller and darker. (4) The Purkinje cell is found in the His bundle, its branches, and the periarterial and subendocardial Purkinje network. © 1993 Wiley-Liss, Inc.     

HISTOPATHOLOGICAL STUDY OF THE CONDUCTION SYSTEM OF THE HEART IN DUCHENNE PROGRESSIVE MUSCULAR DYSTROPHY

The cardiac conduction systems including sinoatrial (SA) node, atrioventricular (AV) node, atrioventricular(His) bundle, and peripheral conduction system (left and right bundle branch, and Purkinje fiber) of 23 patients with Duchenne progressive musculr dystrophy(DMD) were studied with light microscope. Infiltration of fat tissue and mild fibrosis were occasional findings in SA and AV nodes. Degeneration of the conduction muscle fiber was hardly noted in SA node, AV node, and His bundle. Only the peripheral conduction system (Purkinje fiber) showed significant degenerations such as eosinophilic, necrotic and vacuolar changes with fibrosis. These necrobiotic changes resembled hyaline and vacuolar skeletal and cardiac muscular degenerations in DMD and were assumed to have occurred on the basis of the structural and constitutional characteristics of the peripheral conduction fiber as a striated muscle fiber. The vascular changes and amyloid deposit suggesting precocious aging in the conduction systems were not observed.     

Visualization of left ventricular Purkinje fiber distribution using widefield optical coherence microscopy

Background: The distribution and connection of ventricular Purkinje fibers are known to be associated with idiopathic left ventricular arrhythmias. Unusual anatomy is one of the important factors associated with catheter ablation success rate. With the widefield high-speed, swept-source optical coherence microscopy (OCM) and light microscope, we visualized the left ventricular Purkinje fiber distribution. Methods: Left ventricular walls of five adult ovine hearts were incised from the mitral annulus to the apex. Using the widefield OCM technique and light microscopy, we observed the distribution, direction, depth, and dividing patterns of the Purkinje network with multiple tangential angles and without tissue destruction. Results: Widefield OCM was used to characterize the ovine heart Purkinje network system in a 4 × 4 mm² field. Left ventricular Purkinje fibers traveled in the sub-endocardial area near the left-sided peri-membranous septal area and ran like a wide hair bundle. The distal branching fibers penetrated to the endocardium and connected to the contractile muscle. In this distal area, Purkinje fibers were connected to each other, forming multiple layers. Some Purkinje fibers were directly connected within the false tendon between the papillary muscles or between the trabeculations. Some free-running Purkinje fibers were directly connected to the papillary muscle from the left bundle. Conclusion: Using widefield OCM, we were able to observe the left bundle and its branching patterns in ovine left ventricle without tissue destruction. This might be applied to future cardiac ablation procedures.     

牦牛心室蒲肯野纤维的立体分布和结构特点

目的 探讨牦牛心室普肯耶纤维的分布和结构特点,为高原哺乳动物心室传导系统的研究积累形态学资料。 方法 采用墨汁灌注、ABS树脂灌注铸型,石蜡切片HE染色、Masson染色和免疫组织化学染色技术,观察60只成年牦牛的心室普肯耶纤维分布及结构特征。结果 牦牛心室普肯耶纤维束周围包绕有结缔组织鞘。左束支在室间隔内膜下层有2条或3条分支;右束支经隔缘肉柱在右前乳头肌根部心肌层中有3条或4条分支。心室普肯耶纤维在心内膜下层呈多边形网状分布,并在心肌层中发出大量分支,左、右心室乳头肌顶端内膜下层未观察到普肯耶纤维分布。普肯耶纤维呈卷轴状、蜂窝状、漏斗状或脊状构型。Cx43在普肯耶纤维呈膜阳性。结论ABS树脂灌注铸型技术能用于心室普肯耶纤维分布的研究。牦牛心脏左束支和右束支呈不对称分布,左束支较发达。     

家猪房室交界区的组织学观察

利用石蜡切片 ,HE和 Masson染色 ,光镜观测了 7例猪房室交界区的形态学和组织学特征。家猪房室结位于冠状窦口前方 ,大小为 7.0 2× 2 .6 5× 1.2 9mm3。传导细胞分两类 :1细胞短柱状 ,有时有分叉 ,细胞质内有横纹 ,核相对较大 ,此类细胞多位于结上部和前部 ;2典型的移行细胞 ,多位于结的后部和下部。有 2例存在副房室结。结上部和前部、房室束、右束支内的细胞在形态上介于 Purkinje细胞和心肌之间 ,未见典型的 P细胞。说明猪的传导细胞与其它哺乳动物有差异 ,但不同形式的传导细胞却在履行相同的传导功能     

A procedural method for modeling the purkinje fibers of the heart

The Purkinje fibers are located in the ventricular walls of the heart, just beneath the endocardium and conduct excitation from the right and left bundle branches to the ventricular myocardium. Recently, anatomists succeeded in photographing the Purkinje fibers of a sheep, which clearly showed the mesh structure of the Purkinje fibers. In this study, we present a technique for modeling the mesh structure of Purkinje fibers semiautomatically using an extended L-system. The L-system is a formal grammar that defines the growth of a fractal structure by generating rules (or rewriting rules) and an initial structure. It was originally formulated to describe the growth of plant cells, and has subsequently been applied for various purposes in computer graphics such as modeling plants, buildings, streets, and ornaments. For our purpose, we extended the growth process of the L-system as follows: 1) each growing branch keeps away from existing branches as much as possible to create a uniform distribution, and 2) when branches collide, we connect the colliding branches to construct a closed mesh structure. We designed a generating rule based on observations of the photograph of Purkinje fibers and manually specified three terminal positions on a three-dimensional (3D) heart model: those of the right bundle branch, the anterior fascicle, and the left posterior fascicle of the left branch. Then, we grew fibers starting from each of the three positions based on the specified generating rule. We achieved to generate 3D models of Purkinje fibers of which physical appearances closely resembled the real photograph. The generation takes a few seconds. Variations of the Purkinje fibers could be constructed easily by modifying the generating rules and parameters.     

The arterial blood supply of the conducting system in normal human hearts

The distributing artery of the conducting system of the heart is occasionally injured in cardiac surgery. The aim of this study was to define the anatomic characteristics of the principal arterial source of the sinu-atrial node and atrioventricular node. Furthermore, the morphology of the tendon of Todaro was clarified. Thirty hearts were studied by gross anatomic methods, and the exact area of the conducting system was supported by histologic observations of four hearts. The sinu-atrial node was supplied by the right coronary artery more frequently (73% of cases) than by the left (3%), and in 23% of cases this node was supplied by both coronary arteries. The atrioventricular node was supplied by the right coronary artery (80% of cases) more than by the left (10%), and in 10% of the cases this node was supplied by both coronary arteries. The atrioventricular bundle branch arose from the right coronary artery in 10% of cases, the left coronary artery in 73%, and both coronary arteries in 17%. Most of the blood to the right bundle (the moderator band) was supplied by the interventricular septal branches of the anterior interventricular branch from the left coronary artery. Finally, all the arteries of the right bundle and left bundle were defined to be derived from left coronary arteries.     

Two preferential conducting pathways within the bundle of His of the dog heart.

An isolated preparation formed exclusively of the specific conducting tissue of the A. V. node, bundle of His and bundle branches was dissected from the dog heart and studied using the microelectrode technique. The preparation, being completely isolated from the normal neighboring conducting tissues, can be turned over or twisted, so as to stimulate and record either separately or simultaneously the electrical activity of the dorsal and ventral surfaces of the bundle of His. The preparation showed spontaneous activity and maintained its physiological properties for long periods of time. Morphological and electrophysiological evidence was found to differentiate two functional strands within the common trunk of the bundle of His. These two strands appear in different planes: The anterior or ventral strand starts in the superior part of the atrioventricular node and continues to form the right bundle branch; the posterior or dorsal strand begins in the inferior part of the A. V. node and runs underneath the ventral strand to form later the left bundle branch. The two strands can be separated from each other so as to have two functional preparations: one formed of the superior part of the A. V. node, the anterior strand and the right bundle branch; the other constituted by the inferior part of the A. V. node, the posterior strand and the left bundle branch. Some of the electrophysiological properties of both strands are similar, except for the conduction velocity, which appears to be faster in the posterior strand than in the anterior. Transversal propagation occurs between the two strands and is slower than the longitudinal propagation that takes place along the parallel fibers of each strand. The presence of cellular transversal bridges between the strands assures the activation of the two strands as if they were a single conducting cable. These characteristics are discussed in relation to some disturbances in propagation.     

The distribution of atrial natriuretic polypeptide (ANP)-containing cells in the adult rat heart

Summary The present study was performed to clarify the distribution of ANP-containing cells in the adult rat heart by immunostaining for ANP using antiserum against -human ANP. ANP-immunoreactive cells were generally present in the atrial walls except for the sinoatrial node. In the ventricular walls, they were distributed in the impulse conducting system, particularly the left bundle branch, Purkinje fibers on the left side of the interventricular septum, and those in the false tendons in the left ventricle, while they were sporadically seen in the atrioventricular node and bundle of His. The immunoreactive cells contained specific granules that were positive for ANP. These findings demonstrate that ANP-containing cells are present in the atrial and ventricular walls.     

Descriptive anatomy of the dominant septal perforators using Dual Source coronary CT angiography

Although clinical outcomes for septal ablation in treating left ventricular outflow tract obstructions are generally favorable, a variety of complications have been reported including a high incidence of right bundle branch block. These complications may be attributed to anatomic variability of the dominant septal perforator. We used Dual Source CT Coronary Angiography (DS‐CTA) to determine the location of the termination point of the dominant septal perforator as well as the distance of the termination point from the mitral annulus in patients undergoing DS‐CTA. One‐hundred‐fourteen DS‐CTA scans were retrospectively reviewed by two observers by consensus. The left ventricle was divided into anterior wall, anterioseptum, and inferioseptum. For each segment, the myocardium was divided into three layers (1) right ventricular side, (2) mid portion, and (3) left ventricular side. The zone of termination of the dominant septal perforator was identified as well as the distance of the termination point from the mitral annulus. The dominant septal perforator terminated in the right ventricular side of the anterioseptum in 86 of the 118 visualized terminations (73%) and in the left ventricular anterior wall in 6 visualized terminations (5%). On average, the dominant septal perforator terminated 26.3 ± 8.6 mm from the mitral annulus. In the majority of cases, the dominant septal perforator terminates in the right ventricular side of anterioseptum. In addition, there is great variability in the distribution of the termination point of the dominant septal perforator from the mitral annulus. Clin. Anat. 23:70–78, 2010. © 2009 Wiley‐Liss, Inc.     

Topographical and morphometrical study of the atrioventricular junctional area of the cardiac conduction system in the Macaca fascicularis Raffles, 1821

The morphology of the atrioventricular (AV) junctional area is a subject for great controversies. The present work studies this region in 2 hearts of M. fascicularis adult female perfused with Bouin fluid, serial sectioned in frontal plane and stained by van Gieson trichromic method. A three-dimensional wax reconstruction of the AV specialized tissue was performed. The areas of the AV bundle and left bundle branch (LBB) cross-section were calculated by point-counting. The results showed that the junctional AV region in M. fascicularis is approximately similr to the same region in the human heart. The AV node presents compact and transitional portions. The cardiac central fibrous body is well developed and gives off an incomplete septum of connective tissue interposed between the terminal portion of the AV node and the beginning of the AV bundle. The reconstruction showed that the right bundle branch (RBB) is the direct continuation of the AV bundle while the LBB is a broad left side detachment. The average diameters of the AV bundle, LBB and RBB proved to be respectively 867.08 micron and 126.65 micron. The length and the volume of the AV bundle were respectively 406.86 micron and 0.223 mm3.     

Developmental morphology of vascular and lymphatic capillaries in the working myocardium and Purkinje bundle of the sheep septomarginal band

The normal development of vascular and lymphatic capillaries in the right ventricular septomarginal band of the sheep heart was studied in 9 fetuses aged 60-143 days (term = 147 days), 14 lambs aged 1 day to 16 weeks, and 3 adults. Tissue was fixed by perfusion and examined with light and transmission electron microscopy. The septomarginal band is composed of working myocardium and a well-defined peripheral bundle of Purkinje cells. Vascular capillaries of the working myocardium were closely apposed to myocardial cells. By contrast, vascular capillaries of the Purkinje bundle were situated within the connective tissue sheath and septa, at variable distances from the Purkinje cells. After birth, the capillaries of the Purkinje bundle were also found in grooves and tunnels within the Purkinje strands. The ultrastructure of fetal vascular capillaries associated with myocardial and Purkinje cells was initially similar, and characterized by an abundance of synthetic organelles in endothelial cells and pericytes. However, after 115 days in utero, capillary endothelium with diaphragmed fenestrae, 40-60 nm in width, were observed within the Purkinje bundle. The fenestrae attained an average frequency of 1 per 11 capillary cross sections just before term, and this was maintained in lambs and adults. The ultrastructure of lymphatic capillaries, which were not observed in the septomarginal band until just before term, changed little during development.     

Fine structural alteration in the atrioventricular junctional conduction tissues of the dog heart during severe ischaemia

To define the fine structural changes produced in the atrioventricular junctional conduction tissues by severe ischaemia, 3 sets of specimens from 37 dogs were examined by light and electron microscopy using a large specimen resin-embedding method. Surgical control material was taken from 18 open-chest animals maintained under anaesthesia for up to 6 h, autolysis control material from 10 excised normal hearts maintained at 37 degrees C in vitro for up to 4 h, and ischaemic material from 8 animals in which the septal and distal left circumflex coronary arteries were occluded for 15 min to 3 h. Surgical control material was found to be within normal limits, whereas both autolysed and ischaemic showed initially mild fine structural alteration, which increased progressively in severity with time and was comparable in both sets. All cell types showed loss of glycogen granules, mitochondrial swelling, dilatation of sarcoplasmic reticulum vesicles, clumping of nuclear chromatin and ultimately varying degrees of generalised cell swelling. Intramitochondrial dense inclusions also were prominent in autolysis but not ischaemia. These changes progressed faster in nodal cells than in His bundle/bundle branch cells, which retained considerable quantities of glycogen for at least 60 min. The slower development of irreversible alteration in His-Purkinje cells suggests that they may be relatively more resistant to ischaemia, whilst the low incidence of intramitochondrial dense inclusions in vivo suggests a beneficial effect of collateral blood flow.     

A method of study of the pathology of the conduction system for electrocardiographic and his bundle electrogram correlations

There have been advances in electrophysiology which have necessitated a more thorough semi-quantitative analysis of the entire conduction system to yield data useful for correlation purposes. Thus an attempt is made to modify and expand our previous method of studying the conduction system pathologically. This method thus includes the study of the sinoatrial (SA) node and its approaches, the atrial preferential pathways, the approaches to the atrioventricular (AV) node, the AV node, the penetrating and branching portions of the AV bundle, the bundle branches, the peripheral Purkinje nets, and the remainder of the atrial and ventricular myocardium. The SA node and its approaches are studied in a longitudinal manner. This gives a better insight into the pathologic changes than does a study in the transverse direction. The approaches to the AV node, bundle and bundle branches are studied in an oblique manner, rather than horizontally apicalward, or from the posterior to the anterior septal region. The horizontal manner does not give sufficient sampling of the AV node and bundle unless complete serial sections are made. Sectioning from the posterior to the anterior septal wall makes difficult an evaluation of the right bundle branch. In conduction system correlation with Wolff-Parkinson-White and Lown-Ganong-Levine syndromes complete serial sectioning of both AV rims is advisable. Where complete serial sectioning is impossible in large adult hearts, retaining every fifth section may be permissable. In the study of congenitally abnormal hearts, it is advisable to embed the entire heart as a unit. If that is impossible because of the size of the heart, then very careful judicious planning of the fashioning of the blocks is necessary, so that displaced SA nodes, and anterior AV nodes and bundles are not overlooked.     

Morphological study of sarcoplasmic reticulum in the atrioventricular node and bundle cells in guinea pig hearts

The osmium-ferrocyanide method for staining of the sarcoplasmic reticulum (SR) was used for a morphological investigation of the various components of the SR in the atrioventricular node and bundle (AVNB) cells of guinea pig hearts. On the basis of light microscopic observations, the AVNB tissue in guinea pig hearts can be divided into five regions: atrionodal junction, midnode, proximal bundle, distal bundle, and bundle branches. Electron microscopic observations revealed two types of junctional SR (j-SR) saccules in the cells from all the regions of AVNB tissue. One is similar to that seen in the working cardiac cells, i. e., flattened saccules with junctonal granules. The second type is dilated and contains electrondense granular material throughout its lumen. The flattened type is seen more often than the dilated type in atrionodal junctional cells and midnode cells, whereas the dilated type occurs more often in distal bundle cells and bundle branch cells. In most cells from the atrionodal junction and midnode regions, the j-SR saccules are apposed more often to sarcolemmal areas associated with nonspecialized regions of intercellular junctions than to other sarcolemmal areas. This distribution was not found in the distal bundle and bundle branch cells. Free SR tubules around the myofilament bundles are poorly developed in the midnode cells, generally in accord with the extent of development of myofibrils. Z-tubules are found in cells from all regions but are poorly developed in midnode cells. Corbular SR vesicles are found in cells from all the regions of AVNB tissues but are rare in midnode cells. Thus, each of the regions in the AVNB tissue has a different, characteristic distribution of SR components. Because of their possible relationship to the regulation of the intracellular concentrations of calcium, these differences in SR morphology may contribute to the diverse physiological properties of the different regions of the AV node and bundle.