Clarifying the Anatomy of Tetralogy of Fallot with S-shaped Ascending Aorta

We recently encountered several cases of tetralogy of Fallot with an abnormally oriented S-shaped ascending aorta. In this retrospective study, we sought to clarify morphology of this unusual under-recognized variant. Databases were reviewed to identify all patients with tetralogy of Fallot having an S-shaped ascending aorta. Computed tomographic angiography was used for the assessment of cardiac morphology. Out of the 21 patients, 18 (86%) had a right aortic arch, 2 (9%) had a left aortic arch, and the remaining patient (5%) had a double aortic arch. Patients with a right aortic arch, compared to age and sex-matched patients with a right aortic arch but normally oriented ascending aorta, had lesser aortic override (29.3 ± 14% vs 54.8 ± 13.2%; p = 0.0001) and a wider ascending aorta (25.2 ± 6.9 vs 18.0 ± 3.2 mm; p = 0.0003). The S-shaped ascending aorta was located posteriorly, with a higher sterno-aortic distance (25.5 ± 7.7 vs 9.9 ± 4.5 mm; p = 0.0001). The ascending aorta among patients with tortuosity was longer (4.12 ± 1.7 vs 3.07 ± 0.82, p = 0.03) but with similar tortuosity index (1.22 ± 0.19 vs 1.15 ± 0.17, p = 0.23). Of the cases with right aortic arch and S-shaped ascending aorta, 16 (89%) had extrinsic compression of the right pulmonary artery (p = 0.0001), while 7 (39%) had crossed pulmonary arteries (p = 0.008), with no such findings among those with normally oriented ascending aorta. Tetralogy of Fallot with an S-shaped ascending aorta is a variant with lesser aortic override and a more posteriorly located ascending aorta. Compression of the right pulmonary artery and crossed pulmonary arteries is frequent in the presence of a right-sided aortic arch. These findings have important implications for optimal diagnosis and surgical repair.

An unusual form of "haemodynamic vise" in supra cardiac totally anomalous pulmonary venous drainage

We report an unusual variant of obstructed supra cardiac anomalous pulmonary venous drainage where the vertical vein is obstructed by a vice formed between the persistent arterial duct and the left pulmonary artery.

Myocardial Blood Flow Determination From Contrast-Free Magnetic Resonance Imaging Quantification of Coronary Sinus Flow

BACKGROUND

Determination of myocardial blood flow (MBF) with MRI is usually performed with dynamic contrast enhanced imaging (MBFDCE ). MBF can also be determined from coronary sinus blood flow (MBFCS ), which has the advantage of being a noncontrast technique. However, comparative studies of MBFDCE and MBFCS in large cohorts are lacking.

PURPOSE

To compare MBFCS and MBFDCE in a large cohort.

STUDY TYPE

Prospective, sequence-comparison study.

POPULATION

147 patients with type 2 diabetes mellitus (age: 56+/-12 years; 106 male; diabetes duration: 12.9+/-8.1 years), and 25 age-matched controls.

FIELD STRENGTH/SEQUENCES

1.5 Tesla scanner. Saturation recovery sequence for MBFDCE vs. phase-contrast gradient-echo pulse sequence (free-breathing) for MBFCS .

ASSESSMENT

MBFDCE and MBFCS were determined at rest and during coronary dilatation achieved by administration of adenosine at 140 μg/kg/min. Myocardial perfusion reserve (MPR) was calculated as the stress/rest ratio of MBF values. Coronary sinus flow was determined twice in the same imaging session for repeatability assessment.

STATISTICAL TESTS

Agreement between MBFDCE and MBFCS was assessed with Bland and Altman's technique. Repeatability was determined from single-rater random intraclass and repeatability coefficients.

RESULTS

Rest and stress flows, including both MBFDCE and MBFCS values, ranged from 33 to 146 mL/min/100 g and 92 to 501 mL/min/100 g, respectively. Intraclass and repeatability coefficients for MBFCS were 0.95 (CI 0.90; 0.95) and 5 mL/min/100 g. In Bland-Altman analysis, mean bias at rest was -1.1 mL/min/100 g (CI -3.1; 0.9) with limits of agreement of -27 and 24.8 mL/min/100 g. Mean bias at stress was 6.3 mL/min/100 g (CI -1.1; 14.1) with limits of agreement of -86.9 and 99.9. Mean bias of MPR was 0.11 (CI: -0.02; 0.23) with limits of agreement of -1.43 and 1.64.

CONCLUSION

MBF may be determined from coronary sinus blood flow, with acceptable bias, but relatively large limits of agreement, against the reference of MBFDCE .

LEVEL OF EVIDENCE

1 TECHNICAL EFFICACY STAGE: 2.

High-resolution mapping of the circuit of typical atrioventricular nodal reentrant tachycardia

BACKGROUND

Recent anatomic and electrophysiologic evidence has provided new insight into the anatomic substrate. Previous reports on electroanatomic mapping (EAM) of the circuit of atrioventricular nodal reentrant tachycardia (AVNRT) have been limited by mapping only the triangle of Koch on the right side of the septum and by the use of conventional mapping tools. The objectives are to obtain comprehensive high-resolution mapping of typical AVNRT and to investigate the role of the atrioventricular ring tissues in the circuit.

METHODS

We employed EAM with the use of novel modules and algorithms for studying typical AVNRT from the right and the left sides of the septum.

RESULTS

We performed extensive mapping of both the atrial septum and the septal vestibule of the tricuspid valve during typical AVNRT in 9 (6 females) patients, aged 49.6 ± 12.1 years. In two of these, left septal mapping was also obtained through the aorta. The earliest initial activation was variable, emanating from the superior or medial septum. The impulse consistently appeared below the orifice of the coronary sinus, at the site where its inferoanterior margin merged with the septal vestibule of the tricuspid valve at its entrance to the right atrium. It then returned to the initial activation site, presumably through the septal vestibular myocardium. The left septal activation area corresponded to that recorded on the right side.

CONCLUSIONS

Typical AVNRT uses a circuit confined within the pyramid of Koch from the AV node to the septal isthmus, involving the myocardial walls of the pyramidal space.

The clinical anatomy of the atrioventricular conduction axis

It is axiomatic that the chances of achieving accurate capture of the conduction axis and its fascicles will be optimized by equally accurate knowledge of the relationship of the components to the recognizable cardiac landmarks, and we find it surprising that acknowledged experts should continue to use drawings that fall short in terms of anatomical accuracy. The accuracy achieved by Sunao Tawara (1906) in showing the location of the atrioventricular conduction axis is little short of astounding. Our purpose in bringing this to current attention is to question the need of the experts to have produced such inaccurate representations, since the findings of Tawara have been extensively endorsed in very recent years. The recent studies do no more than point to the amazing accuracy of the initial account of Tawara. At the same time, we draw attention to the findings described in the middle of the 20th century by Ivan Mahaim (1947). These observations have tended to be ignored in recent accounts. They are, perhaps, of equal significance to those seeking specifically to pace the left fascicles of the branching atrioventricular bundle.

Development of the arterial roots and ventricular outflow tracts

The separation of the outflow tract of the developing heart into the systemic and pulmonary arterial channels remains controversial and poorly understood. The definitive outflow tracts have three components. The developing outflow tract, in contrast, has usually been described in two parts. When the tract has exclusively myocardial walls, such bipartite description is justified, with an obvious dogleg bend separating proximal and distal components. With the addition of non-myocardial walls distally, it becomes possible to recognise three parts. The middle part, which initially still has myocardial walls, contains within its lumen a pair of intercalated valvar swellings. The swellings interdigitate with the distal ends of major outflow cushions, formed by the remodelling of cardiac jelly, to form the primordiums of the arterial roots. The proximal parts of the major cushions, occupying the proximal part of the outflow tract, which also has myocardial walls, themselves fuse and muscularise. The myocardial shelf thus formed remodels to become the free-standing subpulmonary infundibulum. Details of all these processes are currently lacking. In this account, we describe the anatomical changes seen during the overall remodelling. Our interpretations are based on the interrogation of serially sectioned histological and high-resolution episcopic microscopy datasets prepared from developing human and mouse embryos, with some of the datasets processed and reconstructed to reveal the specific nature of the tissues contributing to the separation of the outflow channels. Our findings confirm that the tripartite postnatal arrangement can be correlated with the changes occurring during development.

Double Outlet of Both Ventricles With an Unusual Relationship of the Great Arteries

Double outlet both ventricles (DOBV) is a rare form of ventriculo-arterial connection wherein the outlet septum is perpendicular to the crest of the apical muscular ventricular septum, thus committing both arterial roots equally to both ventricles. The anomaly has been described in very few reports, with clinical reports being even rarer. We report perhaps the first case of DOBV in which the relationship of the arterial roots themselves is discordant relative to the ventricular topology.

Revisiting the anatomy of the right ventricle in the light of knowledge of its development

Controversies continue regarding several aspects of the anatomy of the morphologically right ventricle. There is disagreement as to whether the ventricle should be assessed in bipartite or tripartite fashion, and the number of leaflets to be found in the tricuspid valve. In particular, there is no agreement as to whether a muscular outlet septum is present in the normally constructed heart, nor how many septal components are to be found during normal development. Resolving these issues is of potential significance to those investigating and treating children with congenitally malformed hearts. With all these issues in mind, we have revisited our own experience in investigating the development and morphology of the normal right ventricle. To assess development, we have examined a large number of datasets, prepared by both standard and episcopic microscopy, from human and murine embryos. In terms of gross anatomy, we have compared dissections of normal autopsied hearts with virtual dissections of datasets prepared using computed tomography. Our developmental and postnatal studies, taken together, confirm that the ventricle is best assessed in tripartite fashion, with the three parts representing its inlet, apical trabecular, and outlet components. The ventricular septum, however, has only muscular and membranous components. The muscular part incorporates a small component derived from the muscularised fused proximal outflow cushions, but this part cannot be distinguished from the much larger part that is incorporated within the free-standing muscular infundibular sleeve. We confirm that the tricuspid valve itself has three components, which are located inferiorly, septally, and antero-superiorly.

The changing morphology of the ventricular walls of mouse and human with increasing gestation

That the highly trabeculated ventricular walls of the developing embryos transform to the arrangement during the fetal stages, when the mural architecture is dominated by the thickness of the compact myocardium, has been explained by the coalescence of trabeculations, often erroneously described as 'compaction'. Recent data, however, support differential rates of growth of the trabecular and compact layers as the major driver of change. Here, these processes were assessed quantitatively and visualized in standardized views. We used a larger dataset than has previously been available of mouse hearts, covering the period from embryonic day 10.5 to postnatal day 3, supported by images from human hearts. The volume of the trabecular layer increased throughout development, in contrast to what would be expected had there been 'compaction'. During the transition from embryonic to fetal life, the rapid growth of the compact layer diminished the proportion of trabeculations. Similarly, great expansion of the central cavity reduced the proportion of the total cavity made up of intertrabecular recesses. Illustrations of the hearts with the median value of left ventricular trabeculation confirm a pronounced growth of the compact wall, with prominence of the central cavity. This corresponds, in morphological terms, to a reduction in the extent of the trabecular layer. Similar observations were made in the human hearts. We conclude that it is a period of comparatively slow growth of the trabecular layer, rather than so-called compaction, that is the major determinant of the changing morphology of the ventricular walls of both mouse and human hearts.

How best can we name the channels seen in the setting of deficient ventricular septation?

Surgical repair of channels between the ventricles is enhanced when the surgeon knows precisely where to place a patch, or baffle, so as to restore septal integrity. The paediatric cardiologist should provide the necessary information. Communication will be enhanced if the same words are used to account for the structures in question. Currently, however, the same term, namely "ventricular septal defect," is used to account for markedly different areas within the heart. Closure of perimembranous defects found in hearts with concordant or discordant ventriculo-arterial connections restores the integrity of the ventricular septum, at the same time separating the systemic and pulmonary blood streams. When both arterial trunks arise from the right ventricle, in contrast, the surgeon when placing a baffle so as to separate the blood streams, does not close the channel most frequently described as the "ventricular septal defect." In this review, we show that the perimembranous lesions as found in hearts with concordant or discordant ventriculo-arterial connections are the right ventricular entrances to the areas subtended beneath the hinges of the leaflets of the aortic or pulmonary valves. When both arterial trunks arise from the right ventricle, and the channel between the ventricles is directly subaortic, then the channel termed the "ventricular septal defect" is the left ventricular entrance to the comparable space subtended beneath the aortic root. We argue that recognition of these fundamental anatomical differences enhances the appreciation of the underlying morphology of the various lesions that reflect transfer, during cardiac development, of the aortic root from the morphologically right to the morphologically left ventricle.

Atrioventricular Septal Defect With Tetralogy of Fallot and Exclusive Shunting at the Ventricular Level

Atrioventricular septal defect (AVSD) with shunting restricted to the ventricular level is a rare form of AVSD. To our knowledge, this shunting pattern has not been reported in AVSD with tetralogy of Fallot. We report a child with this unusual combination who underwent a successful single-stage repair at two years of age.

The Sinus Venosus Veno-Venous Bridge: Not a septal defect

This review provides an update on the morphology of the sinus venosus defect. It was earlier believed that a 'common wall' separated the right pulmonary veins from the superior caval vein. In the sinus venosus defects, this wall was absent. Current evidence shows that the superior rim of the oval fossa, rather than forming a second septum or representing a common wall, is an infolding between the walls of the caval veins and the right pulmonary veins. The sinus venosus defect is caused by the anomalous connection of one or more pulmonary veins to a systemic vein. However, the pulmonary vein(s) retain their left atrial connections, leading to a veno-venous bridge that allows interatrial shunting outside the oval fossa. True atrial septal defects are located within the oval fossa or in the anteo-inferior buttress, while sinus venosus defects, ostium defects and coronary sinus defects are morphologically distinct from them.

Relationship between the aortic root and the atrioventricular conduction axis

Damage to the atrioventricular conduction axis continues to be a problem subsequent to transcatheter implantation of aortic valvar prostheses. Accurate knowledge of the precise relationships of the conduction axis relative to the aortic root could greatly reduce the risk of such problems. Current diagrams highlighting these relationships rightly focus on the membranous septum. The current depictions, however, overlook a potentially important relationship between the superior fascicle of the left bundle branch and the nadir of the semilunar hinge of the right coronary leaflet of the aortic valve. Recent histological investigations demonstrate, in many instances, a very close relationship between the left bundle branch and the right coronary aortic leaflet. The findings also highlight two additional variable features, which can be revealed by clinical imaging. The first of these is the extent of an inferoseptal recess of the left ventricular outflow tract. The second is the extent of rotation of the aortic root within the base of the left ventricle. Much more of the conduction axis is within the confines of the circumference of the outflow tract when the root is rotated in counterclockwise fashion as assessed from the perspective of the imager, with this finding itself associated with a much narrower inferoseptal recess. A clear understanding of the marked variability within the aortic root is key to avoiding future problems with atrioventricular conduction.

The Atrioventricular Conduction Axis Revisited for the 21st Century

Although first described in the final decade of the 19th century, the axis responsible for atrioventricular conduction has long been the source of multiple controversies. Some of these continue to reverberate. When first described by His, for example, many doubted the existence of the bundle we now name in his honour, while Kent suggested that multiple pathways crossed the atrioventricular junctions in the normal heart. It was Tawara who clarified the situation, although many of his key definitions have not universally been accepted. In key studies in the third decade of the 20th century, Mahaim then suggested the presence of ubiquitous connections that provided "paraspecific" pathways for atrioventricular conduction. In this review, we show the validity of these original investigations, based on our own experience with a large number of datasets from human hearts prepared by serial histological sectioning. Using our own reconstructions, we show how the atrioventricular conduction axis can be placed back within the heart. We emphasise that newly emerging techniques will be key in providing the resolution to map cellular detail to the gross evidence provided by the serial sections.

Which Phenotypes Should We Include in the Hypoplastic Left Heart Syndrome?

The recent special issue of the World Journal for Pediatric and Congenital Heart Surgery devoted to hypoplastic left heart syndrome, and its related anomalies, contained significant information of great clinical relevance. Very little attention, however, was devoted to the integrity of ventricular septum as providing a criterion to distinguish between the phenotypes to be included within the syndrome, as opposed to the related anomalies. In this commentary, we summarize the evidence in support of the notion that the phenotypes to be included within the syndrome can be interpreted on the basis of an acquired disease of fetal life. We suggest that it is the integrity of the ventricular septum that provided the major criterion for the distinction between the lesions making up the syndrome and the related anomalies. The subsets of lesions to be included within the syndrome can then be recognized in terms of the time, subsequent to the closure of the embryonic interventricular communication, at which the left ventricle ceased its growth relative to the remainder of the cardiac components. On this basis, it is possible to recognize the combinations of aortic and mitral atresia, mitral stenosis with aortic atresia, combined mitral and aortic stenosis, and hypoplasia of the left ventricle with commensurate hypoplasia of the aortic and mitral valves; the latter combination now recognized as the hypoplastic left heart complex.

The advantages of naming rather than numbering the arteries of the pharyngeal arches

Controversies continue as to how many pharyngeal arches, with their contained arteries, are to be found in the developing human. Resolving these controversies is of significance to paediatric cardiologists since many investigating abnormalities of the extrapericardial arterial pathways interpret their findings on the basis of persistence of a fifth set of such arteries within an overall complement of six sets. The evidence supporting such an interpretation is open to question. In this review, we present the history of the existence of six such arteries, emphasising that the initial accounts of human development had provided evidence for the existence of only five sets. We summarise the current evidence that substantiates these initial findings. We then show that the lesions interpreted on the basis of persistence of the non-existing fifth arch arteries are well described on the basis of the persistence of collateral channels, known to exist during normal development, or alternatively due to remodelling of the aortic sac.

Catheter-induced right bundle branch block: Practical implications for the cardiac electrophysiologist

The right bundle branch (RBB), due to its endocardial course, is susceptible to traumatic block caused by "bumping" during right-heart catheterization. In the era of cardiac electrophysiology, catheter-induced RBB block (CI-RBBB) has become a common phenomenon observed during electrophysiological studies and catheter ablation procedures. While typically transient, it may persist for the entire procedure time. Compared to pre-existing RBBB, the transient nature of CI-RBBB allows for comparative analysis relative to the baseline rhythm. Furthermore, unlike functional RBBB, it occurs at similar heart rates, making the comparison of conduction intervals more reliable. While CI-RBBB can provide valuable diagnostic information in various conditions, it is often overlooked by cardiac electrophysiologists. Though it is usually a benign and self-limiting conduction defect, it may occasionally lead to diagnostic difficulties, pitfalls, or undesired consequences. Avoidance of CI-RBBB is advised in the presence of baseline complete left bundle branch block and when approaching arrhythmic substrates linked to the right His-Purkinje-System, such as fasciculo-ventricular pathways, bundle branch reentry, and right-Purkinje focal ventricular arrhythmias. This article aims to provide a comprehensive practical review of the electrophysiological phenomena related to CI-RBBB and its impact on the intrinsic conduction system and various arrhythmic substrates.

Morphogenetic processes in the development and evolution of the arteries of the pharyngeal arches: their relations to congenital cardiovascular malformations

The heart and aortic arch arteries in amniotes form a double circulation, taking oxygenated blood from the heart to the body and deoxygenated blood to the lungs. These major vessels are formed in embryonic development from a series of paired and symmetrical arteries that undergo a complex remodelling process to form the asymmetric arch arteries in the adult. These embryonic arteries form in the pharyngeal arches, which are symmetrical bulges on the lateral surface of the head. The pharyngeal arches, and their associated arteries, are found in all classes of vertebrates, but the number varies, typically with the number of arches reducing through evolution. For example, jawed vertebrates have six pairs of pharyngeal arch arteries but amniotes, a clade of tetrapod vertebrates, have five pairs. This had led to the unusual numbering system attributed to each of the pharyngeal arch arteries in amniotes (1, 2, 3, 4, and 6). We, therefore, propose that these instead be given names to reflect the vessel: mandibular (1st), hyoid (2nd), carotid (3rd), aortic (4th) and pulmonary (most caudal). Aberrant arch artery formation or remodelling leads to life-threatening congenital cardiovascular malformations, such as interruption of the aortic arch, cervical origin of arteries, and vascular rings. We discuss why an alleged fifth arch artery has erroneously been used to interpret congenital cardiac lesions, which are better explained as abnormal collateral channels, or remodelling of the aortic sac.

A revised terminology for the pharyngeal arches and the arch arteries

The pharyngeal arches are a series of bulges found on the lateral surface of the head of vertebrate embryos. In humans, and other amniotes, there are five pharyngeal arches and traditionally these have been labelled from cranial to caudal-1, 2, 3, 4 and 6. This numbering is odd-there is no '5'. Two reasons have been given for this. One is that during development, a 'fifth' arch forms transiently but is not fully realised. The second is that this numbering fits with the evolutionary history of the pharyngeal arches. Recent studies, however, have shown that neither of these justifications have basis. The traditional labelling is problematic as it causes confusion to those trying to understand the development of the pharyngeal arches. In particular, it creates difficulties in the field of congenital cardiac malformations, where it is common to find congenital cardiac lesions interpreted on the basis of persistence of the postulated arteries of the fifth arch. To resolve these problems and to take account of the recent studies that have clarified pharyngeal arch development, we propose a new terminology for the pharyngeal arches. In this revised scheme, the pharyngeal arches are to be labelled as follows-the first, most cranial, the mandibular (M), the second, the hyoid (H), the third, the carotid (C), the fourth, the aortic (A) and the last, most caudal, the pulmonary (P).

A novel algorithm for classification of interatrial communications within the oval fossa in the newborn

BACKGROUND

An interatrial communication is present in most neonates. The majority are considered the "normal" patency of the oval foramen, while a minority are abnormal atrial septal defects. Differentiation between the two with transthoracic echocardiography may be challenging, and no generally accepted method of classification is presently available. We aimed to develop and determine the reliability of a new classification of interatrial communications in newborns.

METHODS AND RESULTS

An algorithm was developed based on echocardiographic criteria from 495 newborns (median age 11[8;13] days, 51.5% females). The algorithm defines three main categories: patency of the oval foramen, atrial septal defect, and no interatrial communication as well as several subtypes. We found an interatrial communication in 414 (83.6%) newborns. Of these, 386 (93.2%) were categorised as patency of the oval foramen and 28 (6.8%) as atrial septal defects.Echocardiograms from another 50 newborns (median age 11[8;13] days, 36.0% female), reviewed by eight experts in paediatric echocardiography, were used to assess the inter- and intraobserver variation of classification of interatrial communications into patency of the oval foramen and atrial septal defect, with and without the use of the algorithm. Review with the algorithm gave a substantial interobserver agreement (kappa = 0.66), and an almost perfect intraobserver agreement (kappa = 0.82). Without the use of the algorithm, the interobserver agreement between experienced paediatric cardiologists was low (kappa = 0.20).

CONCLUSION

A new algorithm for echocardiographic classification of interatrial communications in newborns produced almost perfect intraobserver and substantial interobserver agreement. The algorithm may prove useful in both research and clinical practice.

The so-called "one-and-a-half" ventricular repair: where are we after 40 years?

OBJECTIVES

The indications, timing, and results of the so-called "one-and-a-half ventricle repair", as a surgical alternative to the creation of the Fontan circulation, or high-risk biventricular repair, currently remain nebulous. We aimed to clarify these issues.

METHODS

We reviewed a total of 201 investigations, assessing selection of candidates, the need for atrial septal fenestration, the fate of an unligated azygos vein and free pulmonary regurgitation, the concerns regarding reverse pulsatile flow in the superior caval vein, the growth potential and function of the subpulmonary ventricle, and the role of the superior cavopulmonary connections as an interstage procedure prior to biventricular repair, or as a salvage procedure. We also assessed subsequent eligibility for conversion to biventricular repair and long-term functional results.

RESULTS

Reported operative mortalities ranged from 3% to 20%, depending on the era of surgical repair with 7% risk of complications due to a pulsatile superior caval vein, up to one-third incidence of supraventricular arrhythmias, and a small risk of anastomotic takedown of the superior cavopulmonary connection. Actuarial survival was between 80% and 90% at 10 years, with two-thirds of patients in good shape after 20 years. We found no reported instances of plastic bronchitis, protein-losing enteropathy, or hepatic cirrhosis.

CONCLUSIONS

The so-called "one-and-a-half ventricular repair", which is better described as production of one-and-a-half circulations can be performed as a definitive palliative procedure with an acceptable risk similar to that of conversion to the Fontan circulation. The operation reduces the surgical risk for biventricular repair and reverses the Fontan paradox.

Expert Consensus Statement: Anatomy, Imaging, and Nomenclature of Congenital Aortic Root Malformations

Over the past 2 decades, several categorizations have been proposed for the abnormalities of the aortic root. These schemes have mostly been devoid of input from specialists of congenital cardiac disease. The aim of this review is to provide a classification, from the perspective of these specialists, based on an understanding of normal and abnormal morphogenesis and anatomy, with emphasis placed on the features of clinical and surgical relevance. We contend that the description of the congenitally malformed aortic root is simplified when approached in a fashion that recognizes the normal root to be made up of 3 leaflets, supported by their own sinuses, with the sinuses themselves separated by the interleaflet triangles. The malformed root, usually found in the setting of 3 sinuses, can also be found with 2 sinuses, and very rarely with 4 sinuses. This permits description of trisinuate, bisinuate, and quadrisinuate variants, respectively. This feature then provides the basis for classification of the anatomical and functional number of leaflets present. By offering standardized terms and definitions, we submit that our classification will be suitable for those working in all cardiac specialties, whether pediatric or adult. It is of equal value in the settings of acquired or congenital cardiac disease. Our recommendations will serve to amend and/or add to the existing International Paediatric and Congenital Cardiac Code, along with the Eleventh iteration of the International Classification of Diseases provided by the World Health Organization.

Recognising ligamentous atresia in double aortic arch

Ligamentous atresia of the left side of a double arch distal to the left subclavian artery is a rare form of vascular ring, which can easily be confused, on transthoracic echocardiography, with the right-sided aortic arch when there is mirror-imaged branching. Because of its rapid acquisition, computed tomographic angiography with three-dimensional reconstruction has now become the modality of choice for accurate diagnosis of the various forms of double aortic arch. It can be performed without sedation in any age group, including neonates. It provides excellent visualisation of the aortic arch and its branching pattern, thus permitting accurate diagnosis and surgical planning. We present a case series of six children with this rare vascular ring assessed using CT, highlighting their outcomes.

Tricuspid atresia and common arterial trunk: a rare form of CHD

Tricuspid atresia with common arterial trunk is a very rare association in complex CHD. This association has even more infrequently been documented concomitantly with interrupted aortic arch. We present the diagnosis and initial surgical management of an infant with a fetal diagnosis of tricuspid atresia and common arterial trunk, with additional postnatal finding of interrupted aortic arch with interruption between the left common carotid and left subclavian artery. Due to the infant's small size, she was initially palliated with bilateral pulmonary artery bands and a ductal stent. This was followed by septation of the common arterial trunk and interrupted aortic arch repair and 4 mm right subclavian artery to main pulmonary artery shunt placement at two months of age. She was discharged home on day of life 81.

Expert Consensus Statement: Anatomy, Imaging, and Nomenclature of Congenital Aortic Root Malformations

Over the past 2 decades, several categorizations have been proposed for the abnormalities of the aortic root. These schemes have mostly been devoid of input from specialists of congenital cardiac disease. The aim of this review is to provide a classification, from the perspective of these specialists, based on an understanding of normal and abnormal morphogenesis and anatomy, with emphasis placed on the features of clinical and surgical relevance. We contend that the description of the congenitally malformed aortic root is simplified when approached in a fashion that recognizes the normal root to be made up of 3 leaflets, supported by their own sinuses, with the sinuses themselves separated by the interleaflet triangles. The malformed root, usually found in the setting of 3 sinuses, can also be found with 2 sinuses, and very rarely with 4 sinuses. This permits description of trisinuate, bisinuate, and quadrisinuate variants, respectively. This feature then provides the basis for classification of the anatomical and functional number of leaflets present. By offering standardized terms and definitions, we submit that our classification will be suitable for those working in all cardiac specialties, whether pediatric or adult. It is of equal value in the settings of acquired or congenital cardiac disease. Our recommendations will serve to amend and/or add to the existing International Paediatric and Congenital Cardiac Code, along with the Eleventh iteration of the International Classification of Diseases provided by the World Health Organization.

Evidence for concealed fasciculo-ventricular connections as revealed by His bundle pacing

BACKGROUND

It 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.

MATERIALS

So 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.

RESULTS

We 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.

CONCLUSIONS

Our 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.

Common Arterial Trunk Coexisting With Double-Barreled Aorta

This case describes the first example of a double-barreled aorta in the setting of a common arterial trunk. Our use of annotated and segmented 3-dimensional models greatly enhanced our ability to elucidate the complex anatomy. (Level of Difficulty: Advanced.).

What Is the Hypoplastic Left Heart Syndrome?

As yet, there is no agreed definition for the so-called "hypoplastic left heart syndrome". Even its origin remains contentious. Noonan and Nadas, who as far as we can establish first grouped together patients as belonging to a "syndrome" in 1958, suggested that Lev had named the entity. Lev, however, when writing in 1952, had described "hypoplasia of the aortic outflow tract complex". In his initial description, as with Noonan and Nadas, he included cases with ventricular septal defects. In a subsequent account, he suggested that only those with an intact ventricular septum be included within the syndrome. There is much to commend this later approach. When assessed on the basis of the integrity of the ventricular septum, the hearts to be included can be interpreted as showing an acquired disease of fetal life. Recognition of this fact is important to those seeking to establish the genetic background of left ventricular hypoplasia. Flow is also of importance, with septal integrity then influencing its effect on the structure of the hypoplastic ventricle. In our review, we summarise the evidence supporting the notion that an intact ventricular septum should now be part of the definition of the hypoplastic left heart syndrome.

Lack of evidence for longitudinal dissociation of the atrioventricular conduction axis

Longitudinal dissociation of the aggregated specialized cardiomyocytes within the non-branching portion of atrioventricular conduction axis has proved a controversial topic for both morphologists and electrophysiologists. We have now used morphological methods, including three-dimensional assessment, to revisit, in human, canine, and bovine hearts, the presence or absence of interconnections between the aggregated cardiomyocytes making up the non-branching bundle. We analyzed three datasets from human and canine hearts, and two from bovine hearts, using longitudinal and orthogonal serial histological sections. In addition, we assessed three hearts using translucent India ink injected specimens, permitting assessment of the three-dimensional arrangement of the cardiomyocytes. Using the longitudinal sections, we found numerous oblique interconnections between the groups of specialized cardiomyocytes. When assessing orthogonal sections, we noted marked variation in the grouping of the cardiomyocytes. We interpreted this finding as evidence of bifurcation and convergence of the groups seen in the longitudinal sections. The three-dimensional assessment of the bovine material confirmed the presence of the numerous interconnections. The presence of multiple connections between the cardiomyocytes in the non-branching bundle rules out the potential for longitudinal dissociation. This article is protected by copyright. All rights reserved.

Chiari network for the interventional cardiologist: A hidden enemy at the heart gate - A systematic review of the literature

BACKGROUND

This study aimed to collect and analyze the literature data regarding Chiari network (CN) and other right atrium (RA) remnants comprising the Eustachian and Thebesian valves (EV, ThV) as a potential entrapment site during different percutaneous cardiac procedures (PCP).

METHODS AND RESULTS

A systematic search was conducted using Pubmed and Embase databases following the PRISMA guidelines to obtain available data concerning PCP associated with entrapment of inserted materials within CN-EV-ThV. The final analysis included 41 patients who underwent PCP with reported material entrapment within these RA remnants. The PCP was atrial septal defect (ASD)/patent foramen ovale (PFO) closure, catheter ablation, and pacemaker/defibrillator implantation in 44%, 22%, and 17% of patients, respectively. The entrapped materials were ASD/PFO devices, multipolar electrophysiology catheters, passive-fixation pacing leads, and J-guidewires in about 30%, 20%, 15%, and 10% of patients, respectively. Intraprocedural transthoracic, transoesophageal and intracardiac echocardiography showed sensitivity to reveal these structures of 20%, ∼95%, and 100%, respectively. A percutaneous approach successfully managed 70% of patients, while cardiovascular surgery was required in 20% and three patients died (7.3%).

CONCLUSIONS

CN and other RA remnants may cause entrapment of various devices or catheters during PCP requiring right heart access. The percutaneous approach, guided by intraprocedural imaging, appears safe and effective in managing most patients. Prevention includes recognizing these anatomical structures at baseline cardiac imaging and intraprocedural precautions. Further studies are needed to analyze the actual incidence of this condition, its clinical impact and appropriate management.

Surgical Repair of a Rare Variant of Common Arterial Trunk, With Considerations of its Significance for Morphogenesis

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.

Vulnerability of the ventricular conduction axis during transcatheter aortic valvar implantation: A translational pathologic study

The ventricular components of the conduction axis remain vulnerable following transcatheter aortic valvar replacement. We aimed to describe features which may be used accurately by interventionalists to predict the precise location of the conduction axis, hoping better to avoid conduction disturbances. We scanned eight normal adult heart specimens by 3T magnetic resonance, using the images to simulate histological sections in order accurately to place the conduction axis back within the heart. We then used histology, tested in two pediatric hearts, to prepare sections, validated by the magnetic resonance images, to reveal the key relationships between the conduction axis and the aortic root. The axis was shown to have a close relationship to the nadir of the right coronary leaflet, in particular when the aortic root was rotated in counterclockwise fashion. The axis was more vulnerable in the setting of a narrow inferoseptal recess, when the inferior margin of the membranous septum was above the plane of the virtual basal ring, and when minimal myocardium was supporting the right coronary sinus. The features identified in our study are in keeping with the original description provided by Tawara, but at variance with more recent accounts. They suggest that the vulnerability of the axis during transcatheter valvar replacement can potentially be inferred on the basis of knowledge of the position of the aortic root within the ventricular base. If validated by clinical studies, our findings may better permit avoidance of new-onset left bundle branch block following transcatheter aortic valvar replacement.

Excessive Trabeculation of the Left Ventricle: JACC: Cardiovascular Imaging Expert Panel Paper

Excessive trabeculation, often referred to as "noncompacted" myocardium, has been described at all ages, from the fetus to the adult. Current evidence for myocardial development, however, does not support the formation of compact myocardium from noncompacted myocardium, nor the arrest of this process to result in so-called noncompaction. Excessive trabeculation is frequently observed by imaging studies in healthy individuals, as well as in association with pregnancy, athletic activity, and with cardiac diseases of inherited, acquired, developmental, or congenital origins. Adults with incidentally noted excessive trabeculation frequently require no further follow-up based on trabecular pattern alone. Patients with cardiomyopathy and excessive trabeculation are managed by cardiovascular symptoms rather than the trabecular pattern. To date, the prognostic role of excessive trabeculation in adults has not been shown to be independent of other myocardial disease. In neonates and children with excessive trabeculation and normal or abnormal function, clinical caution seems warranted because of the reported association with genetic and neuromuscular disorders. This report summarizes the evidence concerning the etiology, pathophysiology, and clinical relevance of excessive trabeculation. Gaps in current knowledge of the clinical relevance of excessive trabeculation are indicated, with priorities suggested for future research and improved diagnosis in adults and children.

Long-Term Surgical Outcomes of Patients With Isomeric Right and Left Atrial Appendages

Objectives: To compare the long-term outcomes of biventricular, univentricular, and so-called one-and-one-half ventricular repairs in patients with left and right isomerism. Methods: Surgical correction was undertaken, between 2000 and 2021, in 198 patients with right, and 233 with left isomerism. Results: The median age at operation was 24 days (interquartile range [IQR]: 18-45) and 60 days (IQR: 29-360) for those with right and left isomerism, respectively. Multidetector computed-tomographic angiocardiography demonstrated more than half of those with right isomerism had superior caval venous abnormalities, and one-third had a functionally univentricular heart. Almost four-fifths of those with left isomerism had an interrupted inferior caval vein, and one-third had complete atrioventricular septal defect. Biventricular repair was achieved in two-thirds of those with left isomerism, but under one-quarter with right isomerism (P < .001). Hazard regression for mortality revealed odds for prematurity at 5.5, pulmonary atresia at 2.81, atrioventricular septal defect with a common valvar orifice at 2.28, parachute mitral valve at 3.73, interrupted inferior caval vein at 0.53, and functionally univentricular heart with a totally anomalous pulmonary venous connection at 3.77. At a median follow-up of 124 months, the probability of survival was 87% for those with left, and 77% for those with right isomerism (P = .006). Conclusions: Multimodality imaging characterizes and delineates the relevant anatomical details, facilitating surgical management of individuals with isomeric atrial appendages. Continuing higher mortality despite surgical intervention in those with right isomerism points to the need for the reassessment of strategies for management.

Anatomy of the mitral valve relative to controversies concerning the so-called annular disjunction

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.

ETS1 loss in mice impairs cardiac outflow tract septation via a cell migration defect autonomous to the neural crest

Ets1 deletion in some mouse strains causes septal defects and has been implicated in human congenital heart defects in Jacobsen syndrome, in which one copy of the Ets1 gene is missing. Here, we demonstrate that loss of Ets1 in mice results in a decrease in neural crest (NC) cells migrating into the proximal outflow tract cushions during early heart development, with subsequent malalignment of the cushions relative to the muscular ventricular septum, resembling double outlet right ventricle (DORV) defects in humans. Consistent with this, we find that cultured cardiac NC cells from Ets1 mutant mice or derived from iPS cells from Jacobsen patients exhibit decreased migration speed and impaired cell-to-cell interactions. Together, our studies demonstrate a critical role for ETS1 for cell migration in cardiac NC cells that are required for proper formation of the proximal outflow tracts. These data provide further insights into the molecular and cellular basis for development of the outflow tracts, and how perturbation of NC cells can lead to DORV.

Persistent Patent Arterial Duct Rather Than a Ligament in the Setting of Diverticulum of Kommerell

We report a rare case of persistent patent arterial duct (PDA) in the combination of diverticulum of Kommerell, aberrant left subclavian artery, and total anomalous pulmonary venous connection (TAPVC). Surgical correction of the defect was done by ligating and dividing the PDA and correcting the TAPVC. (Level of Difficulty: Intermediate.).