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The four heart valves are arranged in different planes from each other. The aortic valve is most centrally located being related to all four cardiac chambers. Similar in construction to the pulmonary valve in possessing semilunar leaflets, neither valve has a ring-like annulus. Instead, the semilunar insertions of the leaflets form a crown-like arrangement. The semilunar valves are complexes comprising not only of leaflets but their attachments to arterial walls and adjoining ventricular structures at the ventriculo-arterial junction. The mitral and tricuspid valves guarding the atrioventricular junctions comprise of leaflets hinged to the junction, and have tendinous cords mainly anchored to papillary muscles that are inserted into ventricular walls to the support apparatus. A complete fibrous annulus is lacking, especially in the tricuspid valve and along the hinge line of the posterior mitral leaflet. This article also reviews the relationships of each valvar component and to adjacent cardiac structures.

Congenitally malformed hearts are often perceived as too complex for the general practitioner. By using a descriptive method, each malformed heart can be analyzed systematically without reference to presumptions of what went wrong during cardiac embryogenesis. The basis of this method, systemic segmental approach, is reviewed followed by examples of the common malformations.

In presenting the essentials of cardiac anatomy for healthcare workers, this article aims to demystify the arrangement of cardiac chambers and valves one to the other. In so doing, it provides better understanding of imaging previously seen in 2 dimensions and in 3 dimensions in the current era. Fundamental to this is the central location of the aorta in relation to all four cardiac chambers. Furthermore, recognition of cardiac chambers is based on distinguishing morphological components irrespective of their location in the heart. Morphological criteria are especially useful in understanding of congenitally malformed hearts.

The supraventricular crest known by its various names is a distinct muscular structure in the normal right ventricle connecting the upper part of the septum to the parietal wall. Its arrangement is disturbed in hearts with tetralogy of Fallot resulting in different names given to its parts. Nevertheless, being comparable location wise to normal implies it has a similar role in the function of the right ventricular and tricuspid valve. Surgical resection of the crest to relief stenosis in tetralogy of Fallot merits reconsideration.

Aims: Supraventricular tachycardia (SVT) is one of the most frequent complications in adult patients with congenital heart disease (CHD). Limited experience exists for successful ablation in complex CHD patients with prior Damus-Kaye-Stansel (DKS) surgery. Methods: All patient files of a single-center were screened retrospectively to identify CHD patients with prior DKS surgery throughout a time-interval from 1998 to 2020. These were analysed with focus on SVT, treatment and outcome of catheter ablation (CA). Results: Overall, 13 patients with prior DKS surgery were identified (median age 22.0 years (IQR 20.5–25.5 years), 76.9% male, 92.3% NYHA Class I, median systemic ventricular ejection fraction 58.5% (IQR 53.0–65.5), 69.2% extra cardiac tunnel). Seven patients (53.8%) presented with symptomatic SVT (median cycle length 440 ms (IQR 360–517 ms)). Of these, five patients underwent CA using remote magnetic navigation. The majority of procedures were performed through a retrograde access using three-dimensional image integration. Median procedure time was 180.5 min (IQR 160.8–274.5 min), median fluoroscopy time 1.5 min (IQR 0.5–4.7 min) and radiofrequency time 851 s (265–2005 s). No peri- or postinterventional complications were observed. After a mean of 1.5 procedures, all patients were complaint-free without documentation of tachycardia recurrence throughout a median follow-up of 13 months (IQR 5.8–17.5 months). Conclusion: In complex univentricular situations after Damus-Kaye-Stansel surgery, ablation for supraventricular tachycardia can be achieved safely and successfully. Techniques such as remote magnetic navigation and three-dimensional image integration may aid for successful procedure results.

Multimodality imaging in cardiology, and particularly congenital heart disease, has evolved into a critical tool, essential for clinical decision-making and management. Understanding the strengths and weaknesses of each imaging modality allows for timely and accurate diagnosis, enables their complementary use in answering specific clinical questions, facilitates management and prevents overuse of cardiovascular imaging ensuring the most appropriate and cost-effective diagnostic strategy for each patient. We provide herewith an expert consensus on the role of different cardiovascular imaging modalities in the assessment of the atrial septal defect and its haemodynamic consequences in adults, highlighting each modality's strengths and weaknesses, and clarifying how they are best applied in various clinical settings.

Transcatheter techniques for the treatment of tricuspid regurgitation (TR) are being more frequently used and several new devices are in development. Since 90% of patients with TR have secondary TR, catheter based systems which reduce the dilated tricuspid annulus area are of particular interest. In order to perform an annuloplasty procedure effectively and safely, knowledge about the anatomy of the tricuspid valve apparatus and especially of the annulus in relation to the important neighboring structures such as the aortic root, the RCA, the electrical pathways and the CS is fundamental. In addition, comprehensive understanding of the device itself, the delivery system, its maneuverability and the individual procedural steps is required. Furthermore, the use of multi-modality imaging is important. For each step of the procedure the appropriate imaging modality as well as the optimal; imaging planes are crucial to provide the necessary information to best guide the individual procedural step.

Even though the tricuspid valve is no longer “forgotten”, it still remains poorly understood. In this review, we focus on some controversial and still unclear aspects of tricuspid anatomy as illustrated by noninvasive imaging techniques. In particular, we discuss the anatomical architecture of the so-called tricuspid annulus with its two components (i.e., the mural and the septal annulus), emphasizing the absence of any fibrous “ring” around the right atrioventricular junction. Then we discussed the extreme variability in number and size of leaflets (from two to six), highlighting the peculiarities of the septal leaflet as part of the septal atrioventricular junction (crux cordis). Finally, we describe the similarities and differences between the tricuspid and mitral valve, suggesting a novel terminology for tricuspid leaflets.

The morphological changes that occur in myxomatous mitral valve disease (MMVD) involve various components, ultimately leading to the impairment of mitral valve (MV) function. In this context, intrinsic mitral annular abnormalities are increasingly recognized, such as a mitral annular disjunction (MAD), a specific anatomical abnormality whereby there is a distinct separation between the mitral annulus and the left atrial wall and the basal portion of the posterolateral left ventricular myocardium. In recent years, several studies have suggested that MAD contributes to myxomatous degeneration of the mitral leaflets, and there is growing evidence that MAD is associated with ventricular arrhythmias and sudden cardiac death. In this review, the morphological characteristics of MAD and imaging tools for diagnosis will be described, and the clinical and functional aspects of the coincidence of MAD and myxomatous MVP will be discussed.

Until recently the treatment of atrial fibrillation (AF) consisted primarily of palliation, mostly in the form of pharmacological intervention. However because of recent advances in nonpharmacologic therapies, the current expectation of patients and referring physicians is that AF will be cured, rather than palliated. In recent years there has been a rapid expansion in the availability and variety of energy sources and devices for ablation. One of these energies, microwave, has been applied clinically only in the last few years, and may be a promising technique that is potentially capable of treating a wide range of ventricular and supraventricular arrhythmias. The purpose of this study was to review microwave energy ablation in surgical treatment of AF with special interest in histology and ultrastructure of lesions produced by this endocardial ablation procedure.

Until recently the treatment of atrial fibrillation (AF) consisted primarily of palliation, mostly in the form of pharmacological intervention. However because of recent advances in nonpharmacologic therapies, the current expectation of patients and referring physicians is that AF will be cured, rather than palliated. In recent years there has been a rapid expansion in the availability and variety of energy sources and devices for ablation. One of these energies, microwave, has been applied clinically only in the last few years, and may be a promising technique that is potentially capable of treating a wide range of ventricular and supraventricular arrhythmias. The purpose of this study was to review microwave energy ablation in surgical treatment of AF with special interest in histology and ultrastructure of lesions produced by this endocardial ablation procedure.

The detailed anatomy of the interatrial septum (IAS) and mitral annulus (MA) as observed on cardiac magnetic resonance, computed tomography and two-dimensional/three-dimensional transthoracic and transesophageal echocardiography is reviewed. The IAS comprises of two components: the septum primum that is membrane-like forming the floor of the fossa ovalis (FO) and the septum secundum that is a muscular rim that surrounds the FO. The latter is an enfolding of atrial wall forming an interatrial groove. Named Waterston's groove, it is filled with adipose tissue on the epicardial side. Thus, the safest area for transseptal puncture (TSP) is within the limits of the FO floor, which provides direct interatrial access. While crossing an intact septum is a well-established procedure, TSP is a more complex and time-consuming procedure in the presence of patent foramen ovalis, aneurysmal FO or atrial septal defect closure devices. MA comprises two distinctive segments: an anterior-straight and a posterior-curved segment. The posterior MA is a thin, discontinuous fibrous 'string', interspersed with adipose tissue, where four components converge: the atrial and ventricular musculature, epicardial adipose tissue and the leaflet's hinge line. In parts of where this fibrous string is deficient or absent, the posterior leaflet is inserted directly on ventricular and atrial myocardium rendering the MA less robust and producing an 'asymmetric' dilation. The marked vulnerability of posterior MA to calcifications might be due to its insertion on the crest of ventricular myocardium being subject to friction injury due to the contraction and relaxation of LV. [ABSTRACT FROM AUTHOR]

A study addressing the problem of human mutations in Nkx2-5 leading to progressive cardiomyopathy and conduction defects via unknown mechanisms, by generating mice with a ventricular muscle cell-restricted knockout of Nkx2-5 is presented. The results show that loss of ventricular muscle cell lineage specification into trabecular and conduction system myocytes is a new mechanistic pathway for cardiomyopathy and conduction defects in congenital heart disease.

Aims The aim of this study is to characterize the arrhythmogenic substrate for peri-mitral atrial flutter (PMAFL), thereby determining a personalized ablation strategy to treat PMAFL. Methods and results Thirty-six consecutive PMAFL patients (mean age: 63.8 ± 11.3, 23 males) underwent detailed three-dimensional electroanatomic mapping in left atrium (LA). The LA was divided into septal-anterior wall (SAW), posterior inferior wall (PIW), and mitral isthmus (MI) region, respectively. Ablation strategy was determined based on the endocardial bipolar voltage map. Based on electrophysiological substrates, 10, 17, and 9 cases were classified into iatrogenic, spontaneous, and no-substrate PMAFL, respectively. The mean voltage in SAW was significantly lower in spontaneous PMAFL (iatrogenic: 1.07 ± 0.66 mV; spontaneous: 0.65 ± 0.44 mV; no-substrate: 1.60 ± 0.53 mV, P <0.001), while iatrogenic PMAFL patients had the lowest voltage in MI (0.51 ± 0.23 mV vs. 1.55 ± 0.78 mV, 1.61 ± 0.56 mV, P <0.001). No low-voltage or slow conduction zone was found in the no-substrate PMAFL group. Fifteen spontaneous PMAFLs were successfully terminated by modified septal-anterior (9/10) or conventional anterior ablation line (6/7). Eight iatrogenic PMAFLs (8/10) were terminated by reinforcing the previous ablation areas. Cardioversion without PMAFL ablation was done in no-substrate PMAFL patients. After a median follow-up of 12 (7–39) months, two spontaneous PMAFL patients received redo procedures for recurrence due to "gap" conduction. Conclusions The ablation strategy for PMAFL patients should be based on the arrhythmogenic substrate, but not the indiscriminate MI ablation. No-substrate PMAFLs during AF ablation could be monitored after cardioversion and might not need further ablation. [ABSTRACT FROM AUTHOR]

Objective: Until now, no study established a morphometric evaluation of the truncal valve dysplasia and a description of its different presentation patterns. Thus, authors conducted an anatomopathological study describing the gross features and histological findings of the truncal valve.Methods: 50 common arterial trunk (CAT) specimens were examined. The number of valvar leaflets was determined and valvar dysplasia was classified as absent, mild, moderate or severe. Selected leaflets were sectioned and submitted to histological analysis and linear measurements (thickness, length and area), besides quantification of collagen area fraction.Results: 28 (56%) valves presented three, 15 (30%) four and 7 (14%) two leaflets. Valvar dysplasia was absent in 13 (26%) cases, mild in 19 (38%), moderate in 6 (12%) and severe in 12 (24%). A significant association was found between the presence of four leaflets and valvar dysplasia (p<0.001). Single coronary ostium was more common in two-leaflet cases than in three-leaflet cases (p=0.037). Leaflets medial thirds were thicker in the more dysplastic valves (p=0.006) and in those presenting anarchic collagen distribution (p=0.002).Conclusions: CAT semilunar valves present two main patterns. The first characterised by three leaflets and absent or mild dysplasia and the second by four leaflets and severe dysplasia. Still, great variability regarding thickness, microscopic organisation of the extracellular matrix and proportions of leaflets' dimensions exists, which may impact on the surgical outcomes. [ABSTRACT FROM AUTHOR]

Aims: Chronic inflammation in the atrial myocardium was shown to play an important role in the development of atrial fibrosis in patients with atrial fibrillation (AF). However, it is not clear to what extent atrial inflammatory reaction associated with AF extends on the ventricular myocardium. Our aim was to assess the extent of fibrosis and lymphomononuclear infiltration in human ventricular myocardium and explore its association with AF.Methods and Results: Medical records from consecutive autopsies were checked for presence of AF. Heart specimens from 30 patients died from cardiovascular causes (64 ± 12 years, 17 men) were collected in three equal groups: no AF, paroxysmal AF, and permanent AF. Tissue samples were taken from the Bachmann's bundle, crista terminalis, posterior left atrium, left ventricle and right ventricle free walls and stained with Masson's trichrome for analysis of fibrosis extent. Immunohistochemistry was performed using antibodies against CD3- and CD45-antigens and quantified as number of antigen-positive cells per 1 mm2. Fibrosis extent, CD3+ and CD45+ cell counts were elevated in AF patients at all sites (P < 0.001 for all). Fibrosis extent demonstrated correlation with both CD3+ and CD45+ cell counts in the right (r = 0.781, P < 0.001 for CD45+ and r = 0.720, P < 0.001 for CD3+) and the left (r = 0.515, P = 0.004 for CD45+ and r = 0.573, P = 0.001 for CD3+) ventricles. Neither fibrosis nor inflammatory cell count showed association with either age or comorbidities.Conclusion: Histological signs of chronic inflammation affecting ventricular myocardium are strongly associated with AF and demonstrate significant correlation with fibrosis extent that cannot be explained by cardiovascular comorbidities otherwise. [ABSTRACT FROM AUTHOR]

Juxtaposition of atrial appendages is a rare cardiac congenital anomaly, usually associated with other cardiac malformations. Until now, it has not been linked to any significant clinical implications. We report cardiovascular magnetic resonance (CMR) findings of two adult patients who underwent atriopulmonary Fontan operation in the setting of left juxtaposition of the atrial appendages. The patients were in sinus rhythm at the time of the CMR study. Both patients had episodes of sustained atrial tachyarrhythmia requiring electrical cardioversion and were anticoagulated with warfarin with target INR 2-3. CMR images showed a thrombus located in the enlarged and juxtaposed right appendage in both patients. Blood flow frequently appears slow or sluggish in the dilated right atrium following atriopulmonary Fontan surgery. In addition, cine CMR suggested that blood flow reaches very low velocities in the massively dilated juxtaposed right atrial appendage cul-de-sac, thus potentially creating a substrate for clot formation. These findings propose that juxtaposed atrial appendages in atriopulmonary Fontan is an additional risk factor for clot formation, specifically in the dilated right atrial appendage on the left side juxtaposed with the left atrial appendage and that prophylactic anticoagulation is highly justified in these patients. [ABSTRACT FROM AUTHOR]

Congenital coronary artery anomalies are of major significance in clinical cardiology and cardiac surgery due to their association with myocardial ischaemia and sudden death. Such anomalies are detectable by imaging modalities and, according to various definitions, their prevalence ranges from 0.21 to 5.79%. This consensus document from the Development, Anatomy and PathologyWorking Group of the European Society of Cardiology aims to provide: (i) a definition of normality that refers to essential anatomical and embryological features of coronary vessels, based on the integrated analysis of studies of normal and abnormal coronary embryogenesis and pathophysiology; (ii) an animal model-based systematic survey of the molecular and cellular mechanisms that regulate coronary blood vessel development; (iii) an organization of the wide spectrum of coronary artery anomalies, according to a comprehensive anatomical and embryological classification scheme; (iv) current knowledge of the pathophysiological mechanisms underlying symptoms and signs of coronary artery anomalies, with diagnostic and therapeutic implications. This document identifies the mosaic- like embryonic development of the coronary vascular system, as coronary cell types differentiate from multiple cell sources through an intricate network of molecular signals and haemodynamic cues, as the necessary framework for understanding the complex spectrum of coronary artery anomalies observed in human patients. [ABSTRACT FROM AUTHOR]

The article focuses on Real-time three dimensional transoesophageal echocardiography (RT 3D TOE) which used as an ultrasound imaging of the heart. providing high quality images of the internal surface of the heart. The article further discusses RT 3D TOE images of the four left atrial structures largely involved in left atrial fibrillation (AF) ablation procedures. As the atrium becomes dilated and fibrotic, structures in addition to pulmonary veins are considered a possible source of AF. INSETS: Potential role of RT 3D TOE during atrial fibrillation...;You can get CPD/CME credits for Education in Heart.

The authors describe the anatomy of left atrium in relation to interventional electrophysiology. Left atrium is located posteriorly and superiorly relative to the right atrial chamber and its posterior part consists of pulmonary veins. A study they conducted on 35 heart specimens revealed that the classic arrangement of four orifices in 74% of pulmonary veins. It has an appendage that is a finger-like pouch smaller than the right side.

Aims: Associated left ventricular structures may play a role in progression and recurrence of discrete subaortic stenosis. The availability of a new 3D echocardiography tool, multiplanar review (MPR), allows comprehensive analysis of datasets in infinite planes, and detailed examination of anatomy. We sought to evaluate the role of MPR in defining the morphology of subaortic stenosis. [ABSTRACT FROM PUBLISHER]

Obstructive lesions in the aortic arch are comprised of discrete coarctation, tubular hypoplasia and interruption. This review discusses the anatomy of the lesions relevant to interventional treatment. Catheter intervention, using not only balloon angioplasty but also stent implantation for coarctation, has been developed over the past couple of decades as an alternative treatment to surgery. Several studies have reported long-term outcome and the benefits of surgery and catheter intervention for treating obstructive lesions in the aortic arch but more studies are needed for comparable evaluations. The development of imaging and further improvement of surgical and catheter intervention, such as hybrid intervention or new devices, will help in removing the obstruction safely. [ABSTRACT FROM AUTHOR]

Transcatheter closure of ventricular septal defects has advanced rapidly with improvements in device designs. We review the morphology of ventricular septal defects in heart specimens for a closer look at the shapes, sizes, and proximity to important structures. The three main types of defects, perimembranous, muscular, doubly committed and juxtaarterial, all have variable morphologies within each group. Oval rather than round shapes are more common. The shapes of muscular defects, in particular, can change from one side of the septum to the other. Perimembranous defects are close to the aortic and tricuspid valves and adjacent to the atrioventricular conduction bundle. Ventricular septal defects are three-dimensional and require careful assessment of proximity to important structures in their vicinity when assessing suitability for interventional closure. [ABSTRACT FROM AUTHOR]

The article focuses on the mechanism of right-to-left atrial shunting despite normal intracardiac pressures and normal or near-normal pulmonary function through a patent foramen ovale. An anatomophysiologic theory to explain the right-to-left shunting with both normal atrial and pulmonary vascular pressures involves the flow phenomenon, but there is still only a limited understanding of its potential significance in relation to right atrial anatomy and physiology. Despite modem diagnostic methods, the underlying anatomophysiologic and pathogenic mechanisms of right-to-left atrial shunting without abnormal intracardiac pressures remain a matter of debate and controversy.

Linear lesions have been proposed for treatment of complex atrial arrhythmias including atrial macroreentry tachycardia and compartmentalization in atrial fibrillation.Aim: To judge the effectiveness of a given lesion design, definite endpoints are necessary to ascertain the completeness of the line of block produced.Methods and results: We report validation criteria for long linear lesions in the right atrium in 42 pts, that combine both conventional and 3D mapping information (CARTO). Transferring from the validation of bi-directional block of the cavotricuspid isthmus line for atrial flutter, we validated 2 additional long linear lesions in the right atrium (anterior line and intercaval line). In addition to a complete isthmus line in all 42 pts, in 28 pts a complete anterior line was achieved and validated by both conventional and CARTO criteria. A complete intercaval line was deployed in 11 pts with complete anterior and isthmus lines (with a characteristic shift for the intercaval line) and in 5 pts without a complete anterior line (without characteristic shift).Conclusions: Conventional catheters placed at strategic locations on opposite sides of the intended ablation line, can depict a sudden characteristic change in the activation sequence. Using a combination of both techniques, deployment and validation of long linear lesion can be facilitated. [ABSTRACT FROM AUTHOR]

Despite the growing trend of device closure for patent ovale foramens (PFO), the morphology of these lesions is much neglected. A better understanding of the morphological aspects is needed for developing lesion-specific devices. We reviewed ten heart specimens and distinguished two forms of PFO: valve competent and valve incompetent. In the valve-competent form, the thin valve of the oval foramen adequately overlaps the firmer muscular rim of the foramen, leaving a crevice-like aperture sandwiched between the two structures. In contrast, the valve-incompetent form results from aneurysmal ballooning of the valve, or stretching of the muscular rim, creating an interatrial communication in a previously competent flap valve. Distinguishing between the two forms can help in designing and selecting the most appropriate device for implantation. [ABSTRACT FROM AUTHOR]

Introduction: Previous mapping studies of right atrial (RA) activation during sinus rhythm have been limited by the use of epicardial electrode plaques in open chest subjects or microelectrodes in the excised heart. This study describes global RA endocardial activation patterns using high-density mapping and compares the results with underlying endocardial architecture. Methods and Results: Noncontact mapping of the RA was performed in 21 anesthetized swine. Isopotential and isochronal maps were superimposed upon three-dimensional reconstructions of RA geometry. Hearts were excised and endocardial dissection performed. Two patterns of RA activation were recorded. The site of earliest endocardial activation occurred either laterally at a position consistent with the terminal crest or superiorly at the junction between the superior caval vein and RA appendage. The subsequent spread of depolarization followed the longitudinal orientation of muscle fibers. Areas of conduction delay and block were seen at the junction between the terminal crest and posterior wall, the cavotricuspid isthmus, and around the margins of the triangle of Koch. Endocardial dissection at these sites demonstrated complex fiber orientation. A lateral site of earliest activation demonstrated a more prominent display of conduction delay or block. Conclusion: The spread of the sinus impulse follows endocardial myofiber orientation and is dictated by the site of earliest activation. Even during sinus rhythm, anisotropic conduction results in areas of conduction block or delay. These findings have implications in the development of reentrant arrhythmias and may influence surgical or electrophysiologic procedures. [ABSTRACT FROM AUTHOR]

Introduction: Anatomic and electrical connections between the left atrium and right atrium (RA) have been described. The relationship between coronary sinus (CS) pacing site and RA activation has not been examined. Methods and Results: Fifteen anesthetized swine underwent high-density noncontact mapping of the RA during pacing from up to five different sites within the CS. Isopotential mapping identified the site of earliest RA depolarization and the pattern of subsequent activation. Hearts were excised and endocardial dissection performed. Earliest RA activation occurred at the CS OS with proximal CS pacing sites and at Bachmann's bundle at distal pacing sites. The mean depth at which a shift in earliest RA activation site occurred was 46 ± 13 mm (range 21 to 63 mm). RA activation times following earliest activation at the CS and Bachmann's bundle were 40 ± 4 msec and 51 ± 6 msec (P < 0.002). Conduction delay or block was recorded at the lateral cavotricuspid isthmus, terminal crest, and tendon of Todaro. Latest RA activation always occurred in the high anterolateral atrium after ascending the anterolateral wall. The lateral RA was activated by the wavefront that traversed the posterior wall rather than by the wavefront crossing the cavotricuspid isthmus, even with earliest RA activation at the CS OS. Conclusion: The site of earliest RA activation during CS pacing is dependent upon the pacing depth within the CS. In the porcine heart, areas of conduction delay influence RA activation patterns and timings. These findings may have implications for patients undergoing assessment of radiofrequency ablation of atrial flutter. [ABSTRACT FROM AUTHOR]

Although knowledge of its existence has barely exceeded one century, the anatomic pathway for conduction of the cardiac impulse from atria to ventricles has been the source of much controversy, controversy that continues to the present day. This article describes bow attention to the original descriptions, along with adherence for sensible definitions for the histological distinction of conduction tissues, could have defused many of these disagreements. One of the problems with the initial descriptions was that they were written in German. Even this is no longer a problem, since the major text devoted to the topic has recently been translated into English, and is now available for all to study. This key work was the monograph produced by Sunao Tawaro, a Japanese pathologist who studied in the first decade of the 20th century in the laboratory of Ludwig Aschoff. Tawara showed that the atrial impulse was conducted to the ventricular myocardium by a solitary pathway of specialized myocardium. He likened this pathway to a tree, with its roots in the base of the atrial septum, and its branches straddling the crest of the muscular ventricular septum. Significantly, he showed that the pathway became insulated as it crossed from atrial to ventricular musculatures, and suggested that the point at which the muscle became engulfed in fibrous tissue should be taken as the boundary between the "knoten," or atrioventricular node, and the penetrating bundle described earlier by Wilhelm His. The authors' findings are entirely compatible with the account given by Tawara. Like Tawara, they recognize atrial transitional cells, a compact node, the penetrating bundle, and the ventricular conduction pathways as the segments of the conduction axis which can be considered to represent the specialized atrioventricular junction. [ABSTRACT FROM AUTHOR]

Introduction: In view of the possible need for septal puncture to ablate left-sided lesions and the occasional difficulty in coronary sinus (CS) cannulation, we investigated relevant anatomic features in the right atrium of hearts with congenitally corrected transposition of the great arteries (ccTGA). Methods and Results: Nine hearts with ccTGA and an intact atrial septum and eight weight-matched normal hearts were examined by studying the "septal" aspect of the right atrium with reference to the oval fossa (OF). The anterior margin was arbitrarily measured as the shortest distance from the OF to the superior mitral/tricuspid annulus. The posterior margin was measured from the OF to the posterior-most edge of the right atrial "septal" surface. The total "septal" surface width was measured at the middle of the OF. The stretched OF dimensions and CS isthmus length were noted. Mann-Whitney test was used to compare absolute and indexed dimensions, i.e.. normalized to total width. The posterior margin in hearts with ccTGA was shorter than in controls (6.3 ± 2.4 mm vs 11 ± 1.9 mm, P < 0.001; normalized margin P = 0.09). The CS isthmus also was significantly shorter (5.3 ± 2.7 mm vs 11.4 ± 2.2 mm, P < O.OO1). In two hearts with ccTGA, the CS opening into the right atrium was on the same side of the eustachian valve as the inferior caval vein. Conclusion: The shorter posterior "septal" margin in hearts with ccTGA may increase the risk of exiting the heart while performing septal puncture when pointing the needle posteriorly. The shorter CS isthmus and the abnormal location of the CS opening in some of these hearts are important when contemplating radiofrequency ablation in this area. [ABSTRACT FROM AUTHOR]

Introduction: Better understanding of atrial propagation during sinus rhythm (SR) in normal hearts under the most normal physiologic conditions may be propaedeutic to pathophysiologic studies of complex atrial arrhythmias. In this study, qualitative and quantitative analyses of sinus impulse propagation in both atria were performed by electroanatomic mapping in patients with no organic heart disease who were undergoing an electrophysiologic procedure. Methods and Results: Seven patients (5 men and 2 women; age 37 ± 11 years) undergoing ablation of a left-sided accessory pathway were considered. Associated heart disease and coexisting atrial arrhythmias were excluded. After obtaining informed consent, electroanatomic mapping of both atria was performed during SR using a nonfluoroscopic system in the postablation phase. Mapping was accomplished in all patients with no complications. Qualitative analysis showed that sinus impulse propagation gives a reproducible activation pattern with minor individual variations. During interatrial propagation, two breakthroughs (anterior and posterior) in the left atrium are observed in the majority of cases. The anterior breakthrough, which reflects conduction over Bachmann's bundle, is predominant and shows a peculiar "preexcitation-like" endocardial activation pattern. Quantitative analysis showed minimal individual variations of propagation time intervals. Atria are activated simultaneously for 65% ± 9% of the duration of the atrial systolic time interval. Conclusion: In normal humans, electroanatomic mapping of SR identifies a typical and reproducible propagation pattern during SR. Bachmann's bundle plays the most important role in interatrial propagation. Atria are activated simultaneously by sinus impulse for a relevant portion of the systolic time interval. [ABSTRACT FROM AUTHOR]

Deals with a study that associated electrophysiologic behavior of the canine atrioventricular (AV) node with the morphologic arrangement of the specialized muscular axis responsible for AV conduction. Dissociation of the electrophysiologic axis for AV conduction; Research literature used by the researchers to establish the difference of AV node and His bundle; Criteria satisfied by cardiac nodes.

Introduction: Radiofrequency catheter ablation carried out in the vicinity of the triangle of Koch risks damaging not only the A V conduction tissues but also their arterial supply. The aim of this study was to examine the relationship of the AV nodal artery to the inferior pyramidal space, the triangle of Koch, and the right atrial endocardial surface. Methods and Results: We studied 41 heart specimens, 24 by gross dissections and 17 by histologic sections. The proximity of the A V nodal artery to the surface landmarks of the triangle of Koch was variable, but it was notable that in 75% of specimens the artery passed close to the endocardial surface of the right atrium and within 0.5 to 5 mm of the mouth of the coronary sinus. In all specimens, the mean distance of the artery to the endocardial surface was 3.5 ± 1.5 mm at the base of Koch's triangle. The location of the compact AV node and its inferior extensions varied within the landmarks of the triangle. At the mid-level of Koch's triangle, the compact node was medially situated in 82% of specimens, but it was closer to the hinge of the tricuspid valve in the remaining 18% of specimens. In 12% of specimens, the inferior parts of the node extended to the level of the mouth of the coronary sinus. Conclusion: The nodal artery runs close to the orifice of the coronary sinus, the endocardial surface of the right atrium, the middle cardiac vein, and the specialized conduction tissues in most hearts. The nodal artery and/or the AV conduction tissues can be at risk of damage when ablative procedures are carried out at the base of the triangle of Koch. [ABSTRACT FROM AUTHOR]

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

Anatomy of Cardiac Nodes. Concomitant with the development or catheter ablation techniques for the treatment of atrial arrhythmias, there is renewed interest In the morpho- logic arrangement of the cardiac conduction system. In this article, we revisit the anatomy of the specialized tissues, making special reference to the descriptions given at the time of their discovery. According to criteria for histologic distinction of morphologically specialized tracts set nearly 100 years ago, the penetrating bundle (of His) and the ventricular bundle branches arc tracts of specialized cells encased by insulating sheaths of fibrous tissue. In contrast, the sinus and AX nodes are recognized histologically but are not insulated from the working atrial myocardium. At its distal extent, the AX node is distinguished from the penetrating bundle not so much by cellular characteristics, but by the presence of a fibrous collar that surrounds the specialized cells. At the atrial part, a zone of histologically transitional cells interposes between the compact node and the working atrial myocardium. Transitional cells enter the triangle of Koch to join the compact node from superiorly, inferiorly, posteriorly, and from the left. Transitional cells of the sinus node, in contrast, are limited to short tongues that interdigitate with musculature of the terminal crest. Apart from a variable extension of Its tail, there are no prominent histologically discrete extensions from the sinus node into the working atrial musculature. The internodal myocardium does not contain discrete conducting tracts comparable with the ventricular bundle branches. Preferential conduction more likely reflects the arrangement of the working internodal cells and their related cellular properties. [ABSTRACT FROM AUTHOR]

Anatomy of Electrophysiologic Isthmus. Introduction: Electrophysiologists recognize a so-called "isthmus" in the right atrium through which passes the reentrant circuit of common atrial flutter. Ablative lesions placed in this narrow channel have proved effective in breaking the circuit. To the best of our knowledge, however, no study has been performed to establish the arrangement and orientation of the atrial myocardial fibers in this crucial area. Methods and Results: We examined 28 normal heart specimens, identifying a quadrilateral area composed of three morphologic sectors between the inferior caval vein and the tri- cuspid valve confluent superiorly with the triangle of Koch. Within this quadrilateral, there are constant recesses, or sinuses, inferior and lateral to the orifice of the coronary sinus. The inferior isthmus measured an average of 31 ± 4 mm (range 19 to 40). Gross examination identified marked differences in the atrial wall forming the quadrilateral. A smooth anterior component forming the vestibule of the tricuspid valve was found in all the hearts, but variations in the remaining sectors were seen in ten specimens. The usually membranous posterior sector was noticeably muscular in three specimens, while the middle, trabecular sector was more membranous in five specimens. We demonstrated the orientation of the subendocardial atrial fibers by dissection In 14 specimens, revealing a relatively constant overall pattern in eight specimens and variations in fiber orientation in the remaining specimens. Conclusion: There are considerable anatomic variations in the atrial wall that comprises the so-called isthmus. The presence of recesses and membranous areas in some hearts and the variations in arrangement of the subendocardial fibers are relevant in improving under- standing of conduction in this area. [ABSTRACT FROM AUTHOR]

Introduction: Recent studies suggest that atrial fibers in the approaches to the AV node form part of the dual pathways recognized electrophysiologically in patients with AV nodal reentrant tachycardia (AVNRT). Our aim was to determine, by gross dissection, the arrangement of the superficial musculature in the area of the triangle of Koch In normal hearts and in hearts with documented AVNRT. hoping to ascertain anatomic features that might con-tribute to the debate. Methods and Results: We used blunt dissection to study the architecture of the superficial atrial musculature in 16 autopsied hearts from adults who died of noncardiac disease. A well-defined pattern of architecture of muscle fibers was found in the region of the triangle of Koch, showing marked variations in 7 of the 16 specimens. The relationship of these fibers to the histologically specialized AV node was confirmed by histology in three cases. Two hearts from patients with known AVNRT, treated by ablation in one, were examined further histologically. These sections showed that the site of ablation was well distant from the histologically discrete AV node. Conclusion: The variability in the arrangement of the superficial atrial muscle fibers in the area of the triangle of Koch may be one of the factors influencing the route for impulses entering the AV node, Lesions that ablate nodal reentry are within these atrial fibers rather than the histologically specialized AV node. [ABSTRACT FROM AUTHOR]

"AV Nodal" Reentry. This review is the first of a two-part series of articles on "atrioventricular [AV] nodal reentry." The early clinical literature as well as the experimental studies are reviewed, and more recent morphologic data are presented. with the aim of clarifying whether the reentrant circuit is confined to the AV node, or consists iii part of extranodal components. Most of the evidence supports the concept that atrial tissue is an essential link in the reentrant pathway. Arguments will be presented to indicate that within the AV node, the separation between antegrade and retrograde pathways is functional, not anatomical, and that both pathways are in electrotonic contact. [ABSTRACT FROM AUTHOR]