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To review the anatomical details, diagnostic challenges, associated cardiovascular anomalies, and techniques and outcomes of management, including re-interventions, for the rare instances of transposition physiology with concordant ventriculo-arterial connections.We reviewed clinical and necropsy studies on diagnosis and surgical treatment of individuals with transposition physiology and concordant ventriculo-arterial connections, analyzing also individuals with comparable flow patterns in the setting of isomerism.Among reported cases, just over two-thirds were diagnosed during surgery, after initial palliation, or after necropsy. Of the patients, four-fifths presented in infancy with either cyanosis or congestive cardiac failure, with complex associated cardiac malformations. Nearly half had ventricular septal defects, and one-fifth had abnormalities of the tricuspid valve, including hypoplasia of the morphologically right ventricle. A small minority had common atrioventricular junctions We included cases reported with isomerism when the flow patterns were comparable, although the atrioventricular connections are mixed in this setting. Management mostly involved construction of intraatrial baffles, along with correction of coexisting anomalies, either together or multistaged. Overall mortality was 25%, with one-fifth of patients requiring pacemakers for surgically-induced heart block. The majority of survivors were in good functional state.The flow patterns produced by discordant atrioventricular and concordant ventriculo-arterial connections remain an important, albeit rare, indication for atrial redirection or hemi-Mustard's procedure with bidirectional Glenn. The procedure recruits the morphologically left ventricle in the systemic circuit, producing good long-term functional results. The approach can also be used for those with isomeric atrial appendages and comparable hemodynamic circuits.

We showed in our anatomical review, ventricular septal defects existing as multiple entities can be considered in terms of three major subsets. We address here the diagnostic challenges, associated anomalies, the role and techniques of surgical instead of interventional closure, and the outcomes, including reinterventions, for each subset.We reviewed 80 published investigations, noting radiographic findings, and the results of clinical imaging elucidating the location, number, size of septal defects, associated anomalies, and the effect of severe pulmonary hypertension.Overall, perioperative mortality for treatment of residual multiple defects has been cited to be between 0% and 14.2%, with morbidity estimated between 6% and 13%. Perioperative mortality is twice as high for perimembranous compared to muscular defects, with the need for reoperation being over four times higher. Perventricular hybrid approaches are useful for the closure of high anterior or apical defects. Overall, the results have been unsatisfactory. Pooled data reveals incidences between 2.8% and 45% for device-related adverse events. Currently, however, outcomes cannot be assessed on the basis of the different anatomical subsets.We have addressed the approaches, and the results, of therapeutic treatment in terms of coexisting discrete defects, the Swiss-cheese septum, and the arrangement in which a solitary apical muscular defect gives the impression of multiple defects when viewed from the right ventricular aspect. Treatment should vary according to the specific combination of defects.

BackgroundIt is almost 100 years ago since Mahaim described the so-called paraspecific connections between the ventricular conduction axis and the crest of the muscular ventricular septum, believing such pathways to be ubiquitous. These pathways, however, have yet to be considered as potential pathways for septal activation during His bundle pacing.MaterialsSo as to explore the hypothesis that specialised septal pathways might provide the substrate for septal activation during His bundle pacing, we compared the findings from 22 serially sectioned histological datasets and 34 different individuals undergoing His bundle pacing.ResultsWe found histologically specialised pathways connecting the branching component of the atrioventricular conduction axis with the crest of the muscular ventricular septum in almost four-fifths of the histological datasets. In 32 of 34 patients undergoing His bundle pacing, the QRS complex closely resembled published images of known conduction through fasciculo-ventricular pathways. In only two patients was a delta wave not seen at any pacing voltages. Capture of these connections varied according to pacing voltage, a finding which correlated with the distance of the pathways from the site of penetration of the ventricular conduction axis. Ventricular activation times remained normal in the presence of the delta wave at higher pacing voltage but were prolonged at lower voltages.ConclusionsOur histologic findings confirm fasciculo-ventricular connections, initially described by Mahaim as being paraspecific, are likely ubiquitous. Analysis of 12-lead electrocardiograms leads us to conclude that fasciculo-ventricular pathways, concealed during sinus rhythm, become manifest with His bundle pacing.

OBJECTIVES The phenotypic features and morphogenesis of the ‘sinus venosus defect’ remain controversial. The phenotypic features are anomalous systemic connections of 1 or more pulmonary veins that retain their left atrial connection, usually associated with a biatrial connection of the superior caval vein. Cases with these features, however, have not always been described as sinus venosus defects. METHODS We reviewed the findings documented in the literature from 11 patients with a biatrial connection of the superior caval vein, most reported following an autopsy examination. We compared these findings with the anatomical details of 50 patients undergoing surgical correction in our centre, paying particular attention to the override of the superior caval vein. RESULTS In only two-thirds of those undergoing surgery did the superior caval vein override the rims of the oval fossa, with the degree of override >50% in only 2 individuals. It is only these latter 2 cases that are directly comparable to the reported cases of biatrial connection of the superior caval vein. CONCLUSIONS Our comparisons provide new insights into the developmental background and phenotypic features of the superior sinus venosus defect. The defects exist because of the anomalous systemic connection of the pulmonary veins that retain their left atrial connections but not always in association with a biatrial connection of the superior caval vein. In extreme cases, nonetheless, they can underscore the connection of the caval vein to the morphologically left atrium, frequently described previously as a ‘biatrial connection’. The sinus venosus defect is better considered a venovenous malformation than a septal defect.

Aims Seeking to account for accessory atrioventricular conduction potentially leading to ventricular pre-excitation, Mahaim in the mid-20th century had described pathways between the atrioventricular conduction axis and the muscular ventricular septum. We aimed to look for such ‘paraspecific’ connections in adult human hearts. Methods and results We serially sectioned 21 hearts, covering the triangle of Koch and the aortic root, and assessing the atrioventricular node, the penetration of the conduction axis, and the bundle branches in our search for fasciculo-ventricular connections. We also calculated the length of the non-branching bundle, and if present the origin of the fasciculo-ventricular connections. The non-branching bundle was 3.6 ± 1.7 mmin length, varying from 1.7 mm to 7.2 mm. Fasciculo-ventricular connections were found in more than half of the hearts, making direct contact with the muscular septum at an average of 3.5 ± 1.7 mm from the origin of the left bundle branch, with the site of origin varying from 1.1 mm to 5.5 mm from the first fascicle of the left bundle branch. In three hearts, additional fasciculo-fascicular connections were observed in the left bundle branch. Two loops were small, but one loop extended over 9.5 mm. Conclusion We endorse the finding of Mahaim that fasciculo-ventricular pathways exist in most human hearts. We presume the identified connections had the capability of producing ventricular pre-excitation. More studies are needed to determine the potential clinical manifestations.

Aims The arrangement of the conduction axis is markedly different in various mammalian species. Knowledge of such variation may serve to question the validity of using animals as prospective models for design of systems for clinical use. Methods and results We compared the arrangement of the atrioventricular conduction axis in human, murine, canine, porcine, and bovine hearts, examining serially sectioned datasets from 20 human, 16 murine, 3 porcine, 5 canine, and 1 bovine hearts. We also analysed computed tomographic datasets obtained from bovines and one human heart. Unlike the situation in the human heart, there is no formation of an atrioventricular fibrous membranous septum in the murine, canine, porcine, nor bovine hearts. Canine, porcine, and bovine hearts also lack an infero-septal recess, when defined as a fibrous plate supporting the buttress of the atrial septum. In these species, half of the non-coronary leaflet is directly opposed to the ventricular septal surface. Conclusion There is a long right-sided non-branching component of the axis, which skirts the attachment of the non-coronary sinus of the aortic root. In the bovine heart, moreover, the left bundle branch usually extends intramyocardially as a solitary tape before surfacing and ramifying on the left ventricular septal surface. The difference in the atrioventricular conduction axis between species may influence the anatomical substrates for atrioventricular re-entry tachycardia, as well as providing inferences for assessing the risks of transcatheter implantation of the aortic valve. Further studies are now needed to assess these possibilities.

Surgeons and electrophysiologists performing accessory pathway ablation procedures have used the term ‘posteroseptal’ region. This area, however, is neither septal nor posterior, but paraseptal and inferior; paraseptal because it includes the fibro-adipose tissues filling the pyramidal space and not the muscular septum itself and inferior because it is part of the heart adjacent to the diaphragm. It should properly be described, therefore, as being inferior and paraseptal. Pathways in this region can be ablated at three areas, which we term right inferior, mid-inferior, and left inferior paraseptal. The right- and left inferior paraseptal pathways connect the right and left atrial vestibules with the right and left paraseptal segments of the parietal ventricular walls. The mid-inferior paraseptal pathways take a subepicardial course from the myocardial sleeves surrounding the coronary sinus and its tributaries. Our review addresses the evolution of the anatomical concept of the inferior paraseptal region derived from surgical and catheter ablation procedures. We also highlight the limitations of the 12-lead electrocardiogram in identifying, without catheter electrode mapping, which are the pathways that can be ablated without a coronary sinus, or left heart approach.

The mid-paraseptal region corresponds to the portion of the pyramidal space whose right atrial aspect is known as the triangle of Koch. The superior area of this mid-paraseptal region is also para-Hisian, and is close to the compact atrioventricular node and the His bundle. The inferior sector of the mid-paraseptal area is unrelated to the normal atrioventricular conduction pathways. It is, therefore, a safe zone in which, if necessary, to perform catheter ablation. The middle part of the mid-paraseptal zone may, however, in some patients, house components of the compact atrioventricular node. This suggests the need for adopting a prudent attitude when considering catheter ablation in this area. The inferior extensions of the atrioventricular node, which may represent the substrate for the slow atrioventricular nodal pathway, take their course through the middle, and even the inferior, sectors of the mid-paraseptal region. In this review, we contend that the middle and inferior areas of the mid-paraseptal region correspond to what, in the past, was labelled by most groups as the ‘midseptal’ zone. We describe the electrocardiographic patterns observed during pre-excitation and orthodromic reciprocating tachycardia in patients with pathways ablated in the middle or inferior sectors of the region. We discuss the modification of the ventriculo-atrial conduction times during tachycardia after the development of bundle branch block aberrancy. We conclude that the so-called ‘intermediate septal’ pathways, as described in the era of surgical ablation, were insufficiently characterized. They should not be considered the surrogate of the ‘midseptal’ pathways defined using endocardial catheter electrode mapping.

The pericardium of the human heart has received increased attention in recent times due to interest in the epicardial approach for cardiac interventions to treat cardiac arrhythmias refractory to conventional endocardial approaches. To support further clinical application of this technique, it is fundamental to appreciate the living anatomy of the pericardial space, as well as its relationships to the surrounding structures. The anatomy of the pericardial space, however, is extremely difficult regions to visualize. This is due to its complex 3-dimensionality, and the “potential” nature of the space, which becomes obvious only when there is collection of pericardial fluid. This potential space, which is bounded by the epicardium and pericardium, can now be visualized by special techniques as we now report, permitting appreciation of its living morphology. Current sources of knowledge are limited to the dissection images, surgical images, and/or illustrations, which are not necessarily precise or sufficient to provide relevant comprehensive anatomical knowledge to those undertaking the epicardial approach. The authors demonstrate, for the first time to their knowledge, the 3-dimensional living anatomy of the pericardial space relative to its surrounding structures. They also provide correlative anatomy of the left sternocostal triangle as a common site for subxiphoid access. The authors anticipate their report serving as a tool for education of imaging and interventional specialists.

The pathways for excitation of the atrioventricular node enter either superiorly, as the so-called ‘fast’ pathway, or inferiorly as the ‘slow’ pathway. However, knowledge of the specific anatomical details of these pathways is limited. Most of the experimental studies that established the existence of these pathways were conducted in mammalian hearts, which have subtle differences to human hearts. In this review, the authors summarise their recent experiences investigating human cardiac development, correlating these results with the arrangement of the connections between the atrial myocardium and the compact atrioventricular node as revealed by serial sectioning of adult human hearts. They discuss the contributions made from the atrioventricular canal myocardium, as opposed to the primary ring. Both these rings are incorporated into the atrial vestibules, albeit with the primary ring contributing only to the tricuspid vestibule. The atrial septal cardiomyocytes are relatively late contributors to the nodal inputs. Finally, they relate our findings of human cardiac development to the postnatal arrangement.

Item does not contain fulltext It is now accepted that the mitral valve functions on the basis of a complex made up of the annulus, the leaflets, the tendinous cords and the papillary muscles. So as to work properly, these components must combine together in harmonious fashion. Despite the features of the arrangement of each component having been the focus of anatomical investigation for centuries, controversies still exist in their inter-relations and how best to describe them. To a large extent, the ongoing problems reflect the fact that, again for centuries, morphologists when describing the heart have ignored the rule that its components should be described as seen in the body during life. Failure to use attitudinally appropriate descriptions underscores a particular current issue, namely the influence of the so-called disjunction within the atrioventricular junction as a potential substrate for leaflet prolapse or malignant arrhythmias. With these difficulties in mind, we have reviewed how the components of the valvar complex can best be described when comparing direct images with those obtained using three-dimensional techniques now used for clinical imaging. We submit that these show that the skirt of leaflet tissue is best described as having aortic and mural components. When the hinge of the mural leaflet is assessed within the overall atrioventricular junction, the so-called disjunction is ubiquitous, but not always in the same place. We further suggest that its significance will best be determined when clinicians describe its presence using attitudinally appropriate terms.

Conduction problems still occur following transcatheter aortic valvar replacement. With this in mind, we have assessed the relationship of the conduction axis to the aortic root. We used serial histological sections, made perpendicular to the base of the triangle of Koch in nine hearts, and perpendicular to the aortic root in 11 hearts. We first defined the extent of the fibrous tissues forming the boundaries of an infero-septal recess of the subaortic outflow tract, found in all datasets but one. When the recess was present, the axis penetrated through its rightward wall, giving rise to the left bundle branch prior to entering the outflow tract. The axis itself was usually on the crest of the ventricular septum, but could be deviated leftward or rightward. Its proximity to the virtual basal plane reflected the angulation of the muscular septum. On average, the superior edge of the left bundle was within 3.3 mm of the hinge of the right coronary leaflet, with a range from 0.4 to 10.2 mm. The arrangement was markedly different in the case lacking an infero-septal recess. Our findings necessitated a redefinition of the right fibrous trigone and the central fibrous body. The atrioventricular conduction axis, having entered the aortic root, is usually closest at the hinge of the right coronary leaflet. Knowledge of the depth of the infero-septal recess, and the angulation of the muscular ventricular septal, may help to avoid conduction problems following transcatheter implantation of the aortic valve.

With the advent of computed tomographic interrogation, it is increasingly frequent to find venous channels that provide direct connections between the pulmonary and systemic veins. These channels, before the introduction of three-dimensional techniques for clinical imaging, were usually found providing an "overflow" for the obstructed left atrium in settings such as hypoplastic left heart syndrome, or divided left atrium. Similar channels, however, had been described almost 100 years ago, with one accurately described as a jugulo-pulmonary vein. Nowadays, however, it is much more usual to find the channels described as levoatrial cardinal veins, even though it is recognized that they are not "levo," often not "atrial," and for sure not "cardinal." In this review, we assemble the evidence supporting the notion that they are better considered as pulmonary-to-systemic collateral channels. We emphasize their similarity, in terms of development, to the sinus venosus and coronary sinus defects.

The Production Assistance for Cellular Therapies (PACT) Program, is funded and supported by the US Department of Health and Human Services’ National Institutes of Health (NIH) National Heart Lung and Blood Institute (NHLBI) to advance development of somatic cell and genetically modified cell therapeutics in the areas of heart, lung, and blood diseases. The program began in 2003, continued under two competitive renewals, and ended June 2021. PACT has supported cell therapy product manufacturing, investigational new drug enabling preclinical studies, and translational services, and has provided regulatory assistance for candidate cell therapy products that may aid in the repair and regeneration of damaged/diseased cells, tissues, and organs. PACT currently supports the development of novel cell therapies through five cell processing facilities. These facilities offer manufacturing processes, analytical development, technology transfer, process scale‐up, and preclinical development expertise necessary to produce cell therapy products that are compliant with Good Laboratory Practices, current Good Manufacturing Practices, and current Good Tissue Practices regulations. The Emmes Company, LLC, serves as the Coordinating Center and assists with the management and coordination of PACT and its application submission and review process. This paper discusses the impact and accomplishments of the PACT program on the cell therapy field and its evolution over the duration of the program. It highlights the work that has been accomplished and provides a foundation to build future programs with similar goals to advance cellular therapeutics in a coordinated and centralized programmatic manner to support unmet medical needs within NHLBI purview.

Aims The exact circuit of atrioventricular nodal re-entrant tachycardia (AVNRT) remains elusive. To assess the location and dimensions of the AVNRT circuit. Methods and results Both typical and atypical AVNRT were induced at electrophysiology study of 14 patients. We calculated the activation time of the fast and slow pathways, and consequently, the length of the slow pathway, by assuming an average conduction velocity of 0.04 mm/ms in the nodal area. The distance between the compact atrioventricular node and the slow pathway ablating electrode was measured on three-dimensionally reconstructed fluoroscopic images obtained in diastole and systole. We also measured the length of the histologically discrete right inferior nodal extension in 31 human hearts. The length of the slow pathway was calculated to be 10.8 ± 1.3 mm (range 8.2–12.8 mm). The distance from the node to the ablating electrode was measured in five patients 17.0 ± 1.6 mm (range 14.9–19.2 mm) and was consistently longer than the estimated length of the slow pathway (P Conclusion Successful ablation affects the tachycardia circuit without necessarily abolishing slow conduction, probably by interrupting the circuit at the septal isthmus.

We honour a great man and a true giant. Lodewyk H.S. van Mierop (March 31, 1927 – October 17, 2021), known as Bob, was not only a Paediatric Cardiologist but also a dedicated Scientist. He made many significant and ground-breaking contributions to the fields of cardiac anatomy and embryology. He was devoted as a teacher, spending many hours with medical students, Residents, and Fellows, all of whom appreciated his regularly scheduled educational sessions. Those of us who were fortunate to know and spend time with him will always remember his great mind, his willingness to share his knowledge, and his ability to encourage spirited and fruitful discussions. His life was most productive, and he will long be remembered by many through his awesome and exemplary scientific contributions.His legacy continues to influence the current and future generations of surgeons and all providers of paediatric and congenital cardiac care through the invaluable archive he established at University of Florida in Gainesville: The University of Florida van Mierop Heart Archive. Undoubtedly, with these extraordinary contributions to the fields of cardiac anatomy and embryology, which were way ahead of his time, Professor van Mierop was a true giant in Paediatric Cardiology. The invaluable archive he established at University of Florida in Gainesville, The University of Florida van Mierop Heart Archive, has been instrumental in teaching medical students, Residents, Medical Fellows, and Surgical Fellows. Only a handful of similar archives exist across the globe, and these archives are the true legacy of giants such as Dr. van Mierop. We have an important obligation to leave no stone unturned to continue to preserve these archives for the future generations of surgeons, physicians, all providers of paediatric and congenital cardiac care, and, most importantly, our patients.

The essence of so-called heterotaxy is the potential disharmony between the arrangement of the bronchuses, abdominal organs, and the atrial appendages. Accurate description of the heart, however, can only be provided by specific description of these features, all of which are readily discernible in the clinical setting. We argue that, when accurate description of the atrial and visceral arrangement is provided, along with appropriate description of the intracardiac findings, no further accuracy is gained by suggesting that an individual heart is “heterotaxic”.

In the human heart, the atrioventricular node is located toward the apex of the triangle of Koch, which is also at the apex of the inferior pyramidal space. It is adjacent to the atrioventricular portion of the membranous septum, through which it penetrates to become the atrioventricular bundle. Subsequent to its penetration, the conduction axis is located on the crest of the ventricular septum, sandwiched between the muscular septum and ventricular component of the membranous septum, where it gives rise to the ramifications of the left bundle branch. In contrast, the bovine conduction axis has a long non‐branching component, which penetrates into a thick muscular atrioventricular septum having skirted the main cardiac bone and the rightward half of the non‐coronary sinus of the aortic root. It commonly gives rise to both right and left bundle branches within the muscular ventricular septum. Unlike the situation in man, the left bundle branch is long and thin before it branches into its fascicles. These differences from the human heart, however, have yet to be shown in three‐dimensions relative to the surrounding structures. We have now achieved this goal by injecting contrast material into the insulating sheaths that surround the conduction network, evaluating the results by subsequent computed tomography. The fibrous atrioventricular membranous septum of the human heart is replaced in the ox by the main cardiac bone and the muscular atrioventricular septum. The apex of the inferior pyramidal space, which in the bovine, as in the human, is related to the atrioventricular node, is placed inferiorly relative to the left ventricular outflow tract. The bovine atrioventricular conduction axis, therefore, originates from a node itself located inferiorly compared to the human arrangement. The axis must then skirt the non‐coronary sinus of the aortic root prior to penetrating the thicker muscular ventricular septum, thus accounting for its long non‐branching course. We envisage that our findings will further enhance comparative anatomical research.

ObjectiveThis study aimed to explore the anatomical features of aortic arch anomalies associated with vascular rings, hoping to identify those which may increase the risk of symptomatic presentation and surgical intervention.MethodsThis was a retrospective observational study at a single cardiac unit. Individuals diagnosed with an aortic arch anomaly, either isolated or non-isolated, between June 2014 and September 2018 were included. The morphology of the aortic arch was established via analysis of postnatal echocardiography, CT or MRI scans. CT and magnetic resonance studies were evaluated for the presence of a Kommerell diverticulum in those with aberrant vessels. Case notes were reviewed for relevant clinical data.ResultsOf those with aberrant subclavian arteries, 24/79 (30.4%) were shown to have a Kommerell diverticulum. Additional forms of congenital heart disease were present in 133/227 (58.6%) individuals. Surgical division of the vascular ring was performed in 30/227 (13.2%), most commonly in the setting of a double aortic arch (70.8%). In those with aberrant subclavian arteries, no children without a Kommerell diverticulum were referred for surgery. In those with a Kommerell diverticulum confirmed on imaging, 11/24 underwent surgery.ConclusionIndividuals with a double aortic arch, or an aberrant subclavian artery arising from a Kommerell diverticulum, have the highest requirement for surgical intervention, especially in isolated anomalies. These individuals should remain under monitoring. The subjective nature of symptoms remains problematic. Longitudinal research is required further to understand the natural history of vascular rings and how it links to morphology.

INTRODUCTION Two-dimensional measurements are self-evidently limited when seeking accurately to represent the three-dimensional complexity of the aortic root. Volumetric measurement, therefore, seems an ideal alternative for a more accurate assessment. MATERIALS AND METHODS We retrospectively analyzed 123 individuals undergoing cardiac computed tomography. We measured the dimensions of the sinuses of Valsalva using routine multiplanar short axis imaging. Three conventional two-dimensional methods were applied to measure the dimensions of the sinuses. These involved bisecting center of sinus-to-center of interleaflet triangle measures, along with center of sinus-to-center of sinus, and largest sinus-to-sinus measurements. We then quantified the volumes of the root using the volume-rendering method. RESULTS The mean dimensions of the sinuses were significantly greater when measured using the largest sinus-to-sinus method as opposed to center of sinus-to-center of interleaflet triangle and center of sinus-to-center of sinus methods (33.6 ± 3.6 mm vs. 31.1 ± 3.1 mm and 30.9 ± 3.3 mm, p

The so-called membranous septum is the fibrous component of the septal structures within the heart. It is relatively subtle in its appearance, but of considerable significance to the understanding of cardiac function and cardiac disease, both congenital and acquired. Surprisingly, its existence was seemingly unknown until the early decades of the 19th century. At this time, those writing in the English language described it as the "undefended space," recognizing its importance in the setting of its aneurysmal dilation, and as the site of septal defects. By the initial decade of the 20th century, it had come to be recognized as the landmark to the site of atrioventricular bundle. Over the first decade of the 21st century, its clinical significance has been emphasized in the context of transcutaneous replacement of the aortic valve. In this review, we describe our own recent investigations of this fibrous part of the septal structures. At the same time, we provide a glimpse of our anatomic past, explaining how its initial description relied on the observations of young physicians taking their first steps in the investigation of cardiac anatomy.

Aims The anatomic substrates for atrioventricular nodal re-entry remain enigmatic, but require knowledge of the normal arrangement of the inputs and exist from the atrioventricular node. This knowledge is crucial to understand the phenomenon of atrioventricular nodal re-entry. Methods and results We studied 20 human hearts with serial sections covering the entirety of the triangle of Koch and the cavotricuspid isthmus. We determined the location of the atrioventricular conduction axis and the connections between the specialized cardiomyocytes of the conduction axis and the adjacent working atrial myocardium. The atrioventricular node was found at the apex of the triangle of Koch, with entry of the conduction axis to the central fibrous body providing the criterion for distinction of the bundle of His. We found marked variation in the inferior extensions of the node, the shape of the node, the presence or absence of a connecting bridge within the myocardium of the cavotricuspid isthmus, the connections between the compact node and the myocardium of the atrial septum, the presence of transitional cardiomyocytes, and the ‘last’ connection between the working atrial myocardium and the conduction axis before it became the bundle of His. Conclusion The observed variations of the inferior extensions, combined with the arrangement of the ‘last’ connections between the atrial myocardium and the conduction axis prior to its insulation as the bundle of His, provide compelling evidence to support the concept for atrioventricular nodal re-entry as advanced by Katritsis and Becker.

Objectives This study sought to describe, in detail, the angiographic, gross macroscopy, and histological dissection of the conduction axis in humans. Background The recent upsurge of interest in specific pacing of the atrioventricular conduction axis has emphasized the need for precise knowledge of the location of the atrial and penetrating components of the atrioventricular conduction axis. Methods A total of 41 human hearts were studied by serial histological sectioning and an additional 3 hearts by gross dissection. One of the hearts studied histologically was also dissected to show the location of the conduction axis prior to serial sectioning. The anatomical findings were then compared with the results of angiography undertaken in the catheter laboratory in 60 patients undergoing electrophysiological studies. Results Marked variation of the location of the transition from atrioventricular conduction axis to the penetrating atrioventricular bundle, or the bundle of His, relative to the landmarks of the triangle of Koch was observed. In just over one-half of both the specimens and the patients, the site of penetration was on the atrial aspect of the hinge of the septal leaflet of the tricuspid valve, with further variation noted relative to the apex of the triangle of Koch. Based on measurements of the histological sections, marked variation in the dimensions of the axis and its adjacency to the right-sided endocardium were also found. In almost three-fifths of hearts, an interventricular component of the fibrous membranous septum was not able to be identified. The significance of these findings to those who seek to perform selective pacing of the atrioventricular conduction axis are discussed. Conclusions Marked variability of the location of the conduction axis within the triangle of Koch is reported. In three-fifths of hearts, the interventricular component of the fibrous membranous septum is nonexistent.

OBJECTIVES Ventricular septal defects can be classified according to their borders or according to the fashion in which they open to the right ventricle, so-called geography. As yet, there is no consensus as to how they should be classified. In an attempt to achieve agreement, the International Society for Nomenclature of Congenital and Paediatric Heart Disease, in 2018, proposed a system incorporating both approaches. We have assessed the subjectivity of their suggested terms hoping to determine their suitability in the desired universal system for classification. METHODS We examined 212 specimens held in the archive of Birmingham Women’s and Children’s Hospital. Each defect was described by 3 independent examiners on the basis of borders and their relationship to the landmarks of the right ventricle. The interobserver agreement was then calculated using Fleiss' method. RESULTS Calculations to assess interobserver agreement showed that the examiners were more likely to agree on the borders of the defects than their so-called geography (κ = 0.804 vs κ = 0.518). The landmarks of the right ventricle proved to be highly variable such that the application of ‘geographic’ terms to hearts with perimembranous defects proved particularly challenging. CONCLUSIONS Interobserver agreement is lower when using terms based on ‘geography’ as opposed to borders. Whilst providing important morphological detail, the terms based on right ventricular landmarks are highly subjective. They should not be prioritized in a universal system of classification. Instead, the defects can be classified simply by using ‘perimembranous’, ‘muscular’, or ‘doubly committed and juxta-arterial’ as first-order terms.

In the December 2021 issue of Cardiology in the Young, Hubrechts and colleagues, from Brussels and Leuven in Belgium, describe their experience in which the pulmonary veins were normally connected to the morphologically left atrium. By virtue of the presence of a shelf dividing the morphologically left atrium, however, the venous return was to the morphologically right atrium, with no evidence of formation of the superior interatrial fold, meaning that there was no obstruction of flow into the systemic venous circulation. The question posed by the Belgian authors is whether the shelf dividing the morphologically left atrium is a deviated primary atrial septum, as the arrangement has previously been interpreted. As they discuss, it is currently impossible to arbitrate this conundrum. In our commentary, we discuss the background to the dilemma. We point out that, as yet, it is not possible to code accurately this congenital cardiac malformation within The International Paediatric and Congenital Cardiac Code (IPCCC), nor within the newly produced 11th Revision of the International Classification of Diseases (ICD-11).

Despite years of research, many details of the formation of the atrioventricular conduction axis remain uncertain. In this study, we aimed to clarify the situation. We studied three-dimensional reconstructions of serial histological sections and episcopic datasets of human embryos, supplementing these findings with assessment of material housed at the Human Developmental Biological Resource. We also examined serially sectioned human foetal hearts between 10 and 30 weeks of gestation. The conduction axis originates from the primary interventricular ring, which is initially at right angles to the plane of the atrioventricular canal, with which it co-localizes in the lesser curvature of the heart loop. With rightward expansion of the atrioventricular canal, the primary ring bends rightward, encircling the newly forming right atrioventricular junction. Subsequent to remodelling of the outflow tract, part of the primary ring remains localized on the crest of the muscular ventricular septum. By 7 weeks, its atrioventricular part has extended perpendicular to the septal parts. The atrioventricular node is formed at the inferior transition between the ventricular and atrial parts, with the transition itself marking the site of the penetrating atrioventricular bundle. Only subsequent to muscularization of the true second atrial septum does it become possible to recognize the definitive node. The conversion of the developmental arrangement into the definitive situation as seen postnatally requires additional remodelling in the first month of foetal development, concomitant with formation of the inferior pyramidal space and the infero-septal recess of the subaortic outflow tract.

OBJECTIVES The most severe combinations of cardiac malformations exist in individuals having jumbled-up thoracic and abdominal organs. These patients make up 2 distinct syndromes. As yet, the consensus is lacking on how best to describe the subsets. The subsets are frequently grouped together in terms of ‘heterotaxy’. The surgical approaches to the subsets, however, are markedly different. We reviewed our experiences with regard to the anatomy as observed in the autopsy room, by the analysis of computed tomographic studies, and in the operating room, to assess whether the lesions might be segregated on the basis of isomerism of the atrial appendages. METHODS AND RESULTS A review of our findings from the examination of specimens from several archives, along with investigation of a large cohort of patients being prepared for surgical treatment, showed that individuals can uniformly be segregated into subgroups on the basis of isomeric arrangement of the atrial appendages. In all instances, this was made possible by using the criterion of the extent of the pectinate muscles within the appendages as judged relative to the atrial vestibules. Segregation on this basis, which correlated excellently with the bronchial arrangement, sets the scene for an appropriate description of the remainder of the heart, providing the cardiac surgeon with all the inferences required for appropriate surgical intervention. CONCLUSIONS When assessing individuals having the features of so-called ‘heterotaxy’, it is possible to segregate the groups into subsets of individuals having either isomeric right or left atrial appendages. This approach provides the framework for the assessment of appropriate surgical management.

The name Ivan Mahaim is well-known to electrophysiologists. However, alternative anatomical substrates can produce the abnormal rhythms initially interpreted on the basis of the pathways he first described. These facts have prompted suggestions that Mahaim should be deprived of his eponym. It is agreed that specificity is required when describing the pathways that produce the disordered cardiac conduction, and that the identified pathways should now be described in an attitudinally appropriate fashion. The authors remain to be convinced that understanding will be enhanced simply by discarding the term ‘Mahaim physiology’ from the lexicon. It is fascinating to look back at the history of accessory atrioventricular junctional conduction pathways outside the normal accessory atrioventricular conduction system, and their possible role in rhythm disturbances. It took both the anatomist and the clinical arrhythmologist quite some time to understand the complex anatomical architecture and the ensuing electrophysiological properties. Over the years, the name Mahaim was often mentioned in those discussions, although these pathways were not the ones that produced the eponym. The reason for this review, therefore, is to present relevant information about the person and what followed thereafter.

We present a successful surgical repair of a rare variant of the common arterial trunk with unusual arrangement of the pulmonary arteries. The variant was not readily classified using either of the popular classifications for the common arterial trunk. It is appropriately described as a common arterial trunk showing aortic dominance, but with extrapericardial origin of the pulmonary arteries from the underside of the truncal arch. We also provide an account of cardiac development, which we suggest offers an accurate explanation for its morphogenesis.

Knowledge of the anatomy of the ‘conduction tissues’ of the heart is a 20th century phenomenon. Although controversies still continue on the topic, most could have been avoided had greater attention been paid to the original descriptions. All cardiomyocytes, of course, have the capacity to conduct the cardiac impulse. The tissues specifically described as ‘conducting’ first generate the cardiac impulse, and then deliver it in such a fashion that the ventricles contract in orderly fashion. The tissues cannot readily be distinguished by gross inspection. Robust definitions for their recognition had been provided by the end of the first decade of the 20th century. These definitions retain their currency. The sinus node lies as a cigar-shaped structure subepicardially within the terminal groove. There is evidence that it is associated with a paranodal area that may have functional significance. Suggestions of dual nodes, however, are without histological confirmation. The atrioventricular node is located within the triangle of Koch, with significant inferior extensions occupying the atrial vestibules and with septal connections. The conduction axis penetrates the insulating plane of the atrioventricular junctions to continue as the ventricular pathways. Remnants of a ring of cardiomyocytes observed during development are also to be found within the atrial vestibules, particularly a prominent retroaortic remnant, although that their role has still to be determined. Application of the initial criteria for nodes and tracts shows that there are no special ‘conducting tissues’ in the pulmonary venous sleeves that might underscore the abnormal rhythm of atrial fibrillation. Sin financiación 7.369 JCR (2021) Q1, 31/143 Cardiac & Cardiovascular Systems 2.146 SJR (2021) Q1, 31/356 Cardiology and Cardiovascular Medicine No data IDR 2021 UEM

Background and aim: On the basis of previously published accounts, coupled with our own experience, we have assessed the surgical approaches to patients with isomeric atrial appendages. Methods: We reviewed pertinent published studies on surgical treatment of individuals with isomeric atrial appendages, with the pertinent surgical details provided by most of the manuscripts. Results: Half of patients with right isomerism, and two-thirds of those with left isomerism have bilateral superior caval veins. Azygos extension of the inferior caval vein is reported in three-quarters of those with left isomerism. The coronary sinus is universally absent in right isomerism, along with totally anomalous pulmonary venous connection, and is absent in two-fifths of those with left isomerism.. Univentricular atrioventricular connections are expected in up to three-quarters of those with right isomerism. Atrioventricular septal defect is reported in up to four-fifths, more frequently in right isomerism, with such patients typically having discordant ventriculoatrial connections or double outlet right ventricle. Reported mortalities extend to 85% for those with right, and 50% for those with left isomerism. In right isomerism, mortality is up to 54% for systemic-to-pulmonary arterial shunting, up to 75% for univentricular repair, and up to 95% for repair of totally anomalous pulmonary venous connection itself. No more than one-quarter had undergone Fontan completion, with reported mortalities of 21%. Conclusion: Early surgical results are satisfactory in patients with left isomerism, but disappointing for those with right. Recent advances in cardiac and liver transplantation may offer improved survival.

The left pulmonary artery arising from the ascending aorta is an infrequent finding. It may be found isolated or with intracardiac anomalies. We present a new case of the left pulmonary artery arising from the ascending aorta and pool these findings with those of previously reported cases. Associated cardiac, extracardiac, and syndromic findings are discussed along with the implications of these in the evaluation and management of this condition.

There is continued interest in surgical repair of both the congenitally malformed aortic valve, and the valve with acquired dysfunction. Aortic valvar repair based on a geometric approach has demonstrated improved durability and outcomes. Such an approach requires a thorough comprehension of the complex 3-dimensional anatomy of both the normal and congenitally malformed aortic root. In this review, we provide an understanding of this anatomy based on the features that can accurately be revealed by contrast-enhanced computed tomographic imaging. We highlight the complimentary role that such imaging, with multiplanar reformatting and 3-dimensional reconstructions, can play in selection of patients, and subsequent presurgical planning for valvar repair. The technique compliments other established techniques for perioperative imaging, with echocardiography maintaining its central role in assessment, and enhances direct surgical evaluation. This additive morphological and functional information holds the potential for improving selection of patients, surgical planning, subsequent surgical repair, and hopefully the subsequent outcomes.

Surgeons, when dividing bypass tracts adjacent to the His bundle, considered them to be ‘anteroseptal’. The area was subsequently recognized to be superior and paraseptal, although this description is not entirely accurate anatomically, and conveys little about the potential risk during catheter interventions. We now describe the area as being para-Hisian, and it harbours two types of accessory pathways. The first variant crosses the membranous septum to insert into the muscular ventricular septum without exiting the heart, and hence being truly septal. The second variant inserts distally in the paraseptal components of the supraventricular crest, and consequently is crestal. The site of ventricular insertion determines the electrocardiographic expression of pre-excitation during sinus rhythm, with the two types producing distinct patterns. In both instances, the QRS and the delta wave are positive in leads I, II, and aVF. In crestal pathways, however, the QRS is ≥ 140 ms, and exhibits an rS configuration in V1–2. The delta wave in V1–2 precedes by 20–50 ms the apparent onset of the QRS in I, II, III, and aVF. In the true septal pathways, the QRS complex occupies ∼120 ms, presenting a QS, W-shaped, morphology in V1–2. The delta wave has a simultaneous onset in all leads. Our proposed terminology facilitates the understanding of the electrocardiographic manifestations of both types of para-Hisian pathways during pre-excitation and orthodromic tachycardia, and informs on the level of risk during catheter ablation.