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R H Anderson

Publications and source records attributed to R H Anderson.

At least 55 records · Page 3Linked to original sources
PubMed2001

Architecture of the pulmonary veins: relevance to radiofrequency ablation.

BACKGROUND: Radiofrequency ablation of tissues in pulmonary veins can eliminate paroxysmal atrial fibrillation. OBJECTIVE: To explore the characteristics of normal pulmonary veins so as to provide more information relevant to radiofrequency ablation. METHODS: 20 structurally normal heart specimens were examined grossly. Histological sections were made from 65 pulmonary veins. RESULTS: The longest myocardial sleeves were found in the superior veins. The sleeves were thickest at the venoatrial junction in the left superior pulmonary veins. For the superior veins, the sleeves were thickest along the inferior walls and thinnest superiorly. The sleeves were composed mainly of circularly or spirally oriented bundles of myocytes with additional bundles that were longitudinally or obliquely oriented, sometimes forming mesh-like arrangements. Fibrotic changes estimated at between 5% and 70% across three transverse sections were seen in 17 veins that were from individuals aged 30 to 72 years. CONCLUSIONS: The myocardial architecture in normal pulmonary veins is highly variable. The complex arrangement, stretch, and increase in fibrosis may produce greater non-uniform anisotropic properties.

Adult↗
PubMed2000

Anatomy of the human atrioventricular junctions revisited.

There have been suggestions made recently that our understanding of the atrioventricular junctions of the heart is less than adequate, with claims for several new findings concerning the arrangement of the ordinary working myocardium and the specialised pathways for atrioventricular conduction. In reality, these claims are grossly exaggerated. The structure and architecture of the pathways for conduction between the atrial and ventricular myocardium are exactly as described by Tawara nearly 100 years ago. The recent claims stem from a failure to assess histological findings in the light of criterions established by Monckeberg and Aschoff following a similar controversy in 1910. The atrioventricular junctions are the areas where the atrial myocardium inserts into, and is separated from, the base of the ventricular mass, apart from at the site of penetration of the specialised axis for atrioventricular conduction. There are two such junctions in the normal heart, surrounding the orifices of the mitral and tricuspid valves. The true septal area between the junctions is of very limited extent, being formed by the membranous septum. Posterior and inferior to this septal area, the atrial myocardium overlies the crest of the ventricular septum, with the atrial component being demarcated by the landmarks of the triangle of Koch. The adjacent structures, and in particular the so-called inferior pyramidal space, were accurately described by McAlpine (Heart and Coronary Arteries, 1975). Thus, again there is no need for revision of our understanding. The key to unravelling much of the alleged controversy is the recognition that, as indicated by Tawara, the atrioventricular node becomes the atrioventricular bundle at the point where the overall axis for conduction penetrates into the central fibrous body. There are also marked differences in arrangement, also described by Tawara, between the disposition of the conduction axis in man as compared to the dog.

Atrioventricular Node↗
PubMed2000

Atrial development in the human heart: an immunohistochemical study with emphasis on the role of mesenchymal tissues.

The development of the atrial chambers in the human heart was investigated immunohistochemically using a set of previously described antibodies. This set included the monoclonal antibody 249-9G9, which enabled us to discriminate the endocardial cushion-derived mesenchymal tissues from those derived from extracardiac splanchnic mesoderm, and a monoclonal antibody recognizing the B isoform of creatine kinase, which allowed us to distinguish the right atrial myocardium from the left. The expression patterns obtained with these antibodies, combined with additional histological information derived from the serial sections, permitted us to describe in detail the morphogenetic events involved in the development of the primary atrial septum (septum primum) and the pulmonary vein in human embryos from Carnegie stage 14 onward. The level of expression of creatine kinase B (CK-B) was found to be consistently higher in the left atrial myocardium than in the right, with a sharp boundary between high and low expression located between the primary septum and the left venous valve indicating that the primary septum is part of the left atrial gene-expression domain. This expression pattern of CK-B is reminiscent of that of the homeobox gene Pitx2, which has recently been shown to be important for atrial septation in the mouse. This study also demonstrates a poorly appreciated role of the dorsal mesocardium in cardiac development. From the earliest stage investigated onward, the mesenchyme of the dorsal mesocardium protrudes into the dorsal wall of the primary atrial segment. This dorsal mesenchymal protrusion is continuous with a mesenchymal cap on the leading edge of the primary atrial septum. Neither the mesenchymal tissues of the dorsal protrusion nor the mesenchymal cap on the edge of the primary septum expressed the endocardial tissue antigen recognized by 249-9G9 at any of the stages investigated. The developing pulmonary vein uses the dorsal mesocardium as a conduit to reach the primary atrial segment. Initially, the pulmonary pit, which will becomes the portal of entry for the pulmonary vein, is located along the midline, flanked by two myocardial ridges. As development progresses, tissue remodeling results in the incorporation of the portal of entry of the pulmonary vein in left atrial myocardium, which is recognized because of its high level of creatine. Closure of the primary atrial foramen by the primary atrial septum occurs as a consequence of the fusion of these mesenchymal structures.

Antibodies, Monoclonal↗
PubMed2000

Relationship in the chick of the developing pulmonary vein to the embryonic systemic venous sinus.

Previous studies have shown that the relationship of the systemic venous sinus (sinus venosus) to the developing pulmonary vein are very similar in mice, rats, and man, with the pulmonary vein gaining access to the heart through a persisting segment of the dorsal mesocardium. It has been suggested that this process differs in avian development, with the pulmonary vein being connected to the systemic venous sinus with subsequent transfer to the left atrium. Here we have investigated the anatomical sequence of events in the chick, using serial histological sections and microdissection followed by scanning electron microscopy. We examined a temporal series of chick embryos, ranging from Hamburger and Hamilton stage 15 to stage 30. Although there are some differences in detail, the development of the pulmonary venous connections in the chick was found to be directly comparable to that already described in eutherian mammals. In both mammals and the chick, the dorsal mesocardial connection, which connects the primitive atrium to the posterior thoracic wall, forms a fixed point through which the pulmonary vein gains access to the atrial compartment of the heart, only varying if the connection itself is anomalous. The tributaries of the systemic venous sinus and the primary atrial septal structures develop around the dorsal connection.

Age Factors↗
PubMed2000

Developmental patterning of the myocardium.

The heart in higher vertebrates develops from a simple tube into a complex organ with four chambers specialized for efficient pumping at pressure. During this period, there is a concomitant change in the level of myocardial organization. One important event is the emergence of trabeculations in the luminal layers of the ventricles, a feature which enables the myocardium to increase its mass in the absence of any discrete coronary circulation. In subsequent development, this trabecular layer becomes solidified in its deeper part, thus increasing the compact component of the ventricular myocardium. The remaining layer adjacent to the ventricular lumen retains its trabeculations, with patterns which are both ventricle- and species-specific. During ontogenesis, the compact layer is initially only a few cells thick, but gradually develops a multilayered spiral architecture. A similar process can be charted in the atrial myocardium, where the luminal trabeculations become the pectinate muscles. Their extent then provides the best guide for distinguishing intrinsically the morphologically right from the left atrium. We review the variations of these processes during the development of the human heart and hearts from commonly used laboratory species (chick, mouse, and rat). Comparison with hearts from lower vertebrates is also provided. Despite some variations, such as the final pattern of papillary or pectinate muscles, the hearts observe the same biomechanical rules, and thus share many common points. The functional importance of myocardial organization is demonstrated by lethality of mouse mutants with perturbed myocardial architecture. We conclude that experimental studies uncovering the rules of myocardial assembly are relevant for the full understanding of development of the human heart.

Animals↗
PubMed2000

Anatomy of the muscular subpulmonary infundibulum with regard to the Ross procedure.

BACKGROUND: To clarify the precise anatomical relationship of the muscular subpulmonary infundibulum. METHODS: Eleven hearts were dissected, and microscopic sections taken through the arterial trunks of a 37-week-old fetus and of a neonate. The anatomy was also investigated during operative Ross procedures. RESULTS: The sinotubular junctions of the pulmonary and aortic roots cross obliquely. The leaflets of the pulmonary valve are lifted away from the ventricular septum by the free-standing subpulmonary infundibulum, whereas the aortic valve is deeply wedged between the atrioventricular junctions. The muscular infundibulum spirals around the aortic root, being longest below the right-facing aortic sinus and shortest below the left. The first septal perforating artery pierces the septum below the shortest part of the infundibulum, sometimes within a millimeter of the pulmonary valvar hinge, but a muscular sleeve lifts the pulmonary leaflets from the septal musculature. CONCLUSIONS: The pulmonary valvar leaflets are supported entirely by free-standing musculature, having no direct relationship with the ventricular septum. This makes possible the Ross procedure.

Adult↗
PubMed2000

Late ventricular structure after partial left ventriculectomy.

Nine months after partial ventriculectomy, a 53-year-old man died of progressive heart failure. His heart was examined to determine the alignment of the muscle fibers around the ventricular scar, which was 11 cm long, 1.3 cm thick and 4 cm wide. The scar reached 2 to 12 mm beyond the surgical suture line. The fibers in the middle and subendocardial layers were malaligned, resulting in convergence, compression and regional necrosis.

Cardiomyopathy, Alcoholic↗
PubMed2000

The anatomy of interatrial communications--what does the interventionist need to know?

Increasingly, the interventional cardiologist is seeking to close interatrial communications by inserting devices by means of catheterisation. So as to optimise these procedures, it is advantageous to have a firm grasp of the anatomy of the normal atrial septal structures, this then providing the basis to understand the morphology of the holes which can exist between the chambers, not all of which are true septal defects. A true septal structure can be removed without exiting from the cavities of the heart. It is the flap valve of the oval fossa, along with the anterior rim of the fossa, which fulfill this criterion. The remainder of the extensive rim of the normal fossa is no more than an infolding between the walls of the right and left atria and their venous tributaries, and has different dimensions at various points around the circumference. The so-called muscular atrioventricular "septum" is a sandwich incorporating a layer of epicardial fibro-adipose tissue. True defects of the atrial septum, therefore, exist because of deficiency, perforation, or absence of the flap valve. Most of these defects will prove suitable for interventional closure, but potential caveats include multiple defects, aneurysm of the flap valve, or adjacency of the fossa to the venous orifices. The other interatrial communications, namely the sinus venosus, coronary sinus, and "ostium primum" defects are outside the confines of the oval fossa. Recognition of this feature is the key to their diagnosis, and their differentiation from true atrial septal defects. Of these defects, only the coronary sinus defect is likely to be suitable for device closure, and then only in the very rare circumstances when it is seen in isolation.

Cardiac Catheterization↗
PubMed2000

Twisted atrioventricular connections in double inlet right ventricle: evaluation by magnetic resonance imaging.

Twisted atrioventricular connections occur almost exclusively in the hearts with biventricular atrioventricular connections. Only one example of double inlet left ventricle has been illustrated in which the axes of the two atrioventricular valves crossed each other. We describe herein three patients, and one autopsied specimen, with double inlet right ventricle in which magnetic resonance imaging clearly demonstrated twisted atrioventricular connections.

Child, Preschool↗
PubMed2000

Transthoracic three-dimensional echocardiography for the assessment of straddling tricuspid or mitral valves.

BACKGROUND: The advent of 3D echocardiography has provided a technique which, potentially, could afford significant additional information over conventional cross-sectional echocardiography in the assessment of patients with straddling atrioventricular valves prior to surgical correction. METHODS: Eight patients, aged from 1 month to 9.2 years, were examined with 3D echocardiography. All but three had discordant ventriculoarterial connections or double outlet right ventricle. Data suitable for reconstruction was acquired with transthoracic scanning. Right and left ventricular volumes were calculated in the 3D dataset. RESULTS: 3D echocardiography proved capable of defining the exact degree of straddling by imaging the proportion of tension apparatus attached to either side of the ventricular septum. It was able also to display the atrioventricular junction "en face", thus permitting identification of the precise site of insertion of the muscular ventricular septum relative to the atrioventricular junction. This made it possible first, to calculate the degree of valvar override, and second, to predict the location of the penetrating atrioventricular bundle. End-diastolic volume of the right ventricle in those with straddling tricuspid valves was 73 (61-83)% of normal, and, of the left ventricle in those with mitral valvar straddling 71 (40-97)% of normal. CONCLUSIONS: 3D echocardiography can aid in planning the optimal surgical procedure in patients with straddling or overrriding atrioventricular valves, as it provides diagnostic information superior to standard cross-sectional techniques. It also allows for exact measurement of the volumes of the respective ventricles.

Child↗
PubMed2000

How constant anatomically is the tendon of Todaro as a marker for the triangle of Koch?

INTRODUCTION: Although well recognized by anatomists as a border of the triangle of Koch demarcating the location of the AV node, the tendon of Todaro is not visible in the operating room or in the catheterization laboratory. Instead, clinicians use as surrogate a projected line between the eustachian valve and the central fibrous body. The constancy of the tendon of Todaro within this border remains to be determined. MATERIALS AND RESULTS: We reexamined serial histologic sections from 25 adults and 50 infants and gross dissections in four normal hearts. The tendon of Todaro was identified in all cases and traced to the central fibrous body in all but one case. It tended to be thicker in the hearts of infants cases (0.2 to 0.8 mm vs 0.1 to 0.6 mm). The tendon and the hinge-line of the septal leaflet of the tricuspid valve were consistent as landmarks for location of the compact AV node in all the cases studied by histology. Gross dissections traced the tendon to the free edge of the eustachian valve. CONCLUSION: The tendon of Todaro is present in hearts obtained from both adults and infants. It, or its surrogate, is a reliable border for the triangle of Koch and serves as a landmark to location of the atrial components of the AV conduction axis.

Adolescent↗
PubMed2000

Coronary arterial origins in transposition of the great arteries: factors that affect outcome. A morphological and clinical study.

OBJECTIVE: Transfer of the coronary arteries is crucial during the arterial switch operation for transposition, but little attention has been paid to the position of their orifices relative to the valvar sinuses. The objective of this study was to determine the factors which are important for effective transfer and to determine potential surgical significance. DESIGN: Morphological and clinical study. SETTING: Two national centres for neonatal cardiac surgery. PATIENTS: 277 patients with transposition of the great arteries. One group comprised 88 necropsy specimens (ages ranging from 17 weeks of fetal life to 17 years old), and the other comprised 189 children undergoing surgery. The coronary artery orifices were inspected relative to the depth of the aortic sinuses (vertical origin), relative to the commissures between the valvar leaflets (radial origin), and their angle of exit from the aortic wall (angle of origin). The data were compared with the surgical results. RESULTS: In the necropsy specimens, the vertical origin of the arteries was at, or above, the sinutubular junction in 20%, the radial origin was paracommissural in 3%, and the angle of origin was not orthogonal in 7%. Those with high take off and paracommissural origin were all intramural. In the clinical cases, those children with high take off, paracommissural origin or tangential origin had an increased risk at surgery. CONCLUSIONS: In 20% of hearts, high take off, paracommissural orifice, or tangential origin of coronary arteries is found. This may be recognised preoperatively by echocardiography and may cause technical difficulty in transfer during the arterial switch procedure.

Child↗
PubMed2000

The atrioventricular junctions in Ebstein malformation.

OBJECTIVE: To review the anatomical structure of the right atrioventricular junction, including the specialised atrioventricular conduction system, in hearts with Ebstein's malformation, to identify potential substrates for the abnormalities in conduction. METHODS: Five heart specimens representing the morphological spectrum of Ebstein malformation were examined grossly and histologically. RESULTS: On the endocardial surface, the atrioventricular junction was marked by a faint line in two hearts, and by a small ridge in the other three. Analysis of the right parietal junction in four hearts revealed only two accessory muscular atrioventricular connections. A plane of fibrofatty tissue separated atrial from ventricular myocardium in the right parietal junction in all hearts. The compact atrioventricular node was closer to the coronary sinus than usual. Accessory nodoventricular connections were present in four hearts, while accessory fasciculo-ventricular connections were found in one. The right bundle branch was hypoplastic or absent in four hearts. CONCLUSIONS: In this small series, the parietal atrioventricular junction was better developed than previously thought. Structural abnormalities of the atrioventricular conduction system, however, were present. These may account for some of the conduction abnormalities frequently observed with the Ebstein malformation.

Atrioventricular Node↗