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Background —Although most ablative procedures undertaken for common atrial flutter target the inferior right atrial isthmus, comparative studies of the morphology of this area are lacking. Our study examines its angiographic anatomy, making correlations with postmortem specimens, to provide a better understanding of the anatomic substrate of this arrhythmia. Methods and Results —The gross morphological features and dimensions of the area between the orifice of the inferior caval vein and the attachment of the septal leaflet of the tricuspid valve were determined from angiograms made in 23 patients with documented atrial flutter and 30 control subjects. For comparison, we studied 20 normal heart specimens. When viewed in right anterior oblique projection, 2 morphologically distinct areas were identified. In the specimens, the inferior isthmus measured a mean length of 30±4 mm, not significantly different from the dimensions obtained from angiograms of control subjects. The mean length of the isthmus, however, was greater in patients with common atrial flutter than those without (37±8 versus 28±6 mm). Patients with atrial flutter and structural heart disease had an even longer isthmus than those with flutter alone (39.6±8 versus 33±7 mm). Compared with those without flutter, the atrial diameter was also larger in patients with flutter (57.6±9 versus 48.5±6 mm). Reevaluation carried out at follow-up 10±2 months after ablation did not show any reduction in atrial size, although contractility improved. Conclusions —The inferior isthmus and right atrium in patients with common atrial flutter were significantly larger than those in a control population.

OBJECTIVE—To evaluate the feasibility of anatomical correction based on morphological and echocardiographic findings in patients and preserved hearts with discordant atrioventricular connections. DESIGN—A retrospective study with clinicomorphological correlations to assess potential contraindications for anatomical correction in the setting of discordant atrioventricular connections. SETTING—A tertiary referral centre for congenital heart disease. MATERIAL—25 specimens and 53 patients unified by presence of discordant atrioventricular connections. METHODS—The potential contraindications for anatomical correction were first evaluated on the basis of morphological findings in all 25 specimens with discordant atrioventricular connections collected in the department museum, including study of the major coronary arterial patterns in 20. These contraindications were then sought in a population of 53 patients examined echocardiographically between January 1992 and October 1997. RESULTS—At least one lesion was discovered that might have contraindicated anatomical correction in 14 of the specimens and in 16 of the patients. The most common lesions that might militate against the anatomical approach were severe Ebstein's malformation or straddling and overriding of the tricuspid valve, each when combined with hypoplasia of the morphologically right ventricle. Other potential contraindications were atrioventricular septal defect with common atrioventricular junction, and obstruction of the left ventricular outlet combined with a restrictive ventricular septal defect, although these may be overcome with increasing experience and expertise. CONCLUSIONS—According to the morphological and echocardiographic findings, at least 10 hearts and 37 patients would have produced no anatomical problems for the type of surgical correction in which the morphologically left ventricle is restored its rightful role as the systemic pumping chamber. Keywords: atrioventricular discordant connections; congenitally corrected transposition; double switch operation

Objective—To study patients with atrioventricular septal defect to determine the pathognomonic morphological features of the lesion and the relation between the septal structures and the atrioventricular junction. Setting —Tertiary level paediatric cardiology centre. Methods—Cross sectional echocardiograms from 60 patients were reviewed using qualitative and quantitative analysis. The unifying feature was the presence of a common atrioventricular junction. The overall dimensions of the septal defect were determined and related to the plane of the common junction; the extent of both the atrial and the ventricular septal components was then measured according to the site of closure of the bridging leaflets. Results—In 48 cases, the common junction was guarded by a common valvar orifice, but in 12 cases there were separate right and left valvar orifices. Irrespective of the valvar morphology, no significant difference was found between the groups in terms of the dimensions of the atrial and ventricular septal components. In all patients, the hole permitting shunting at atrial level extended below the plane of the atrioventricular junction, with a variable position of the leading edge of the atrial septum itself. Conclusions—The atrioventricular junction is a common structure irrespective of valvar morphology. In spite of the presence of unequivocal shunting at atrial level, the atrial septum is usually a well formed structure, even extending in some below the level of the common atrioventricular junction. Keywords: atrioventricular canal malformation; endocardial cushion defects; level of shunting; morphology

Aims Our aim was to clarify the location and structure of the outlet septum relative to the free-standing sub-pulmonary infundibulum in the setting of tetralogy of Fallot and to examine its relationship to the other components of the subpulmonary outflow tract, determining their potential influence on clinical outcome. Methods and Results We studied prospectively 41 patients with tetralogy of Fallot (mean age 14±10·9 months) prior to surgical repair, and compared them with 15 patients undergoing closure of a ventricular septal defect associated with malalignment of the outlet septum but no subpulmonary infundibular stenosis (Eisenmenger ventricular septal defect), and 20 healthy controls. We also examined available autopsied hearts from cases with uncorrected tetralogy of Fallot (8) and Eisenmenger ventricular septal defect (13). Data were indexed for body surface area, and diameter of the tricuspid valve, respectively. The overall length of the subpulmonary infundibulum, including the extent of the muscular outlet septum, was significantly greater for patients with tetralogy of Fallot compared to normals (2·34±0·6 vs 1·46±0·34cm/BSA0·5, P

Objective: Our aim was to elucidate the morphologic spectrum of Ebstein's malformation of the tricuspid valve with regard to diagnosis and the feasibility of surgical repair, in the light of the currently favored reconstructive techniques. Methods: We examined 23 autopsied hearts. Taking the displacement of the septal and mural leaflets of the abnormal tricuspid valve as our diagnostic criterion, we focused subsequently on the location of the distorted valvular orifice and the attachment and formation of the anterosuperior leaflet. We also assessed the dimensions of the components of the right ventricle relative to the plane of the displaced valvular orifice. Results: In all hearts, the septal and mural leaflets were hinged at various points within the inlet of the right ventricle. In many cases, however, these leaflets were virtually absent. The plane of the effective tricuspid valvular orifice was displaced anterosuperiorly to varying degrees. In the most severe forms, the valvular mechanism took the form of a 1-leaflet valve. The length of the functional right ventricle when compared with the left ventricle ranged proportionally from 0.6 to 1.1 (mean, 0.9). Conclusions: Ebstein's malformation is much more than simple "downward displacement" of the leaflets. In essence, the valvular orifice is formed within the ventricular cavity at the junction of the atrialized inlet and functional ventricular components. When surgical intervention becomes necessary, it is essential to make a detailed assessment of both valvular and ventricular abnormalities. (J Thorac Cardiovasc Surg 1999;117:148-55)

The aim of the present study was to advance our knowledge regarding the anatomy of the purkinje fibres from their origin, at the bundle branches, till their termination within the myocardium. Indian ink injections of the purkinje fibres were carried out in the left ventricle of 25 fresh sheep hearts and in the right ventricle of 20 hearts. Numerous samples were taken from the walls and papillary muscles of the two ventricles for histological analysis and determination of the mode of termination of the fibres. The ventricular conduction system could be injected as far proximally as the bundle branches, thus illustrating the bifascicular nature of the left bundle branch, with numerous interfascicular communications. The purkinje fibres were observed to form an extensive subendocardial network, forming a polygonal arrangement in the left ventricle with a characteristic pattern around the papillary muscles. Deep myocardial branches took origin from this network which penetrated the ventricular wall to reach the epicardium. Histological analysis demonstrated the characteristic features of the purkinje cells, and confirmed the presence ofa perifascicular sheath of connective tissue which surrounded the purkinje fibres until their transition with working cardiomyocytes. The perifascicular connective tissue sheath is important in organising the contraction of the myocardium by preventing lateral spread of conduction and by permitting transmission of the impulse only at the termination of the purkinje fibre. The sheath may also protect the fibres from the stresses and strains originating from contraction of the surrounding myocardium.

An apparently healthy man of 26 years of age suddenly died. He was known to have had a small ventricular septal defect and complete right bundle branch block from early childhood. At post-mortem examination the small ventricular septal defect was found associated with an aneurysm of the membranous septum. Histological examination showed a normal atrioventricular node and bundle, adjacent to the aneurysm. There was fibrous interruption at the commencement of the right bundle branch, which was considered the basis of the bundle branch block. It was also considered that the right bundle branch block was of the hereditary type and that this, rather than the aneurysm of the membranous septum, was responsible for the unexpected death.

By definition, accessory atrioventricular pathways are aberrant muscle bundles that connect the atrium to a ventricle outside of the regular atrioventricular conduction system. Clinically, they may manifest as substrates for ventricular preexcitation. The first accessory pathway in a patient who suffered from Wolff-Parkinson-White syndrome was described in 1943 by Wood, Wolferth, and Geckler.1 Shortly after, Ohnell created a reconstruction of an accessory pathway that very elegantly showed the close proximity of the pathway to the fibrous attachment of the mitral valve and its relationship with the sulcus coronarius (Figure, A).2 Subsequent histological studies have demonstrated unequivocally that these pathways are the anatomic substrates for the classical Wolff-Parkinson-White variety of preexcitation. Figure. A, Ohnell’s depiction of an accessory bundle in the left atrioventricular groove.2 Reprinted with permission from Blackwell Publishing. B, Histological section stained with Masson’s trichrome (fibrous tissue in green and myocardium in red) to show an accessory left-sided pathway (arrow) skirting the mitral annulus. C, Histological section showing a broad right-sided accessory pathway (arrow) that is formed by a myocardial pouch extending from the right atrial appendage to the ventricle and ultimately traced to a small right ventricular vein. This pathway is some distance from the fibrous annulus of the tricuspid valve. *Valvar annulus. Article p 1508 Accessory atrioventricular pathways are found most often in the parietal atrioventricular junctional areas, including the paraseptal areas. They breach the insulation provided by the fibrofatty tissues of the atrioventricular groove (sulcus tissue) and the hingelines (fibrous annulus) of the valves. They are rarely found in the area of fibrous continuity between the aortic and mitral valves because in this area, there is usually a wide gap between the atrial myocardium and ventricular myocardium to accommodate the aortic outflow tract. On the left parietal side, the accessory pathways tend …

Concomitant with the development of catheter ablation techniques for the treatment of atrial arrhythmias, there is renewed interest in the morphologic 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 are tracts of specialized cells encased by insulating sheaths of fibrous tissue. In contrast, the sinus and AV nodes are recognized histologically but are not insulated from the working atrial myocardium. At its distal extent, the AV 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.

Little attention has been paid to whether the interventricular communication in complete atrioventricular septal defect is different beneath the superior and inferior bridging leaflets, a feature of obvious surgical significance. We searched for a defect under the bridging leaflets and examined the valve morphologies in 98 autopsied and 86 surgical patients. Of the overall specimens, 27 were associated with Fallot's tetralogy, and a further 20 had subaortic stenosis, aortic coarctation, or both. In the autopsied specimens, we also measured the degree of deficiency of the ventricular septum. No communication was found under the inferior bridging leaflet in 30% (29 of 98) of the specimens. All 29 hearts except two without such communications showed an undivided inferior leaflet. In contrast, all patients undergoing operation except 1 had a communication beneath both bridging leaflets (p < 0.001). The absence of a communication beneath the inferior leaflet was observed more in hearts with Fallot's tetralogy (seven of 14) or those with subaortic stenosis, aortic coarctation, or both (eight of 18) than in those without associated anomalies (14 of 66; p < 0.01). Those with a communication under the inferior leaflet showed a greater deficiency of the inlet ventricular septum than did those without it (p < 0.001). In a certain percentage of patients with complete atrioventricular septal defect, there will be no communication under the inferior bridging leaflet. Surgeons should be aware of this possibility, particularly when confronted with a patient with obstruction in either ventricular outlet

Background . The surgical option of biventricular repair requires two ventricles, each fully capable of supporting the systemic or pulmonary circulation. The morphologic substrates that may preclude some hearts from biventricular repair need to be assessed. Methods . Heart specimens were reviewed to assess the morphologic mechanisms that produce an unbalanced ventricular mass and to identify features that would, potentially, be a contraindication for biventricular repair. Results . Hearts with solitary and indeterminate ventricles, and hearts with essentially solitary ventricles, often have associated abnormalities of venoatrial connections and arrangement of the atrioventricular valves. In the majority of hearts with univentricular atrioventricular connections, the rudimentary and incomplete ventricle of either right or left morphology may be too small to support either the systemic or the pulmonary circulation. Straddling with overriding of the atrioventricular valve, unbalanced atrioventricular septal defect, and gross hypoplasia of one of the ventricles in hearts with biventricular connections are other mechanisms producing ventricular imbalance, which could preclude biventricular repair. Conclusions . The morphologic mechanisms that result in ventricular imbalance are mainly related to the sizes and morphology of the ventricles, septal malalignment, valvar morphology, and component make-up of the ventricles. These features will influence decision-making in considering the option of biventricular repair.

Background . In hearts having the atriums connected only to a dominant left ventricle, typified by double-inlet left ventricle but seen also in lesions such as tricuspid atresia, subaortic obstruction, when it exists, is usually found at the level of the ventricular septal defect when the aorta is supported by the rudimentary right ventricle. Methods . Heart specimens were examined to determine the nature and position of the ventricular septal defect existing between dominant left and rudimentary right ventricles when the ventriculoarterial connections are discordant. Results . Most commonly, the ventricular septal defect is positioned between the muscular apical trabecular septum and the muscular outlet septum. This type of defect is found not only in double-inlet left ventricle, but also in hearts with absence of either the right or left atrioventricular connection when the other atrium is connected to a dominant left ventricle, irrespective of the position of the rudimentary and incomplete right ventricle. Obstructive lesions within the aortic arch are commonly associated with restriction at the site of the ventricular septal defect. The atrioventricular conduction bundle takes a constant course relative to the margin of the septal defect. Conclusions . Because subaortic obstruction is almost always caused by a restrictive ventricular septal defect, relief of the obstruction can be achieved by surgical enlargement of the septal defect, bearing in mind the course of the atrioventricular conduction system.

Background . The concept of "one and a half" ventricular repair is to use "half" a ventricle to support the pulmonary circulation. The component makeup of any ventricle needs clarification for us to understand the nature of the so-called half ventricle. Methods . The components of normal and abnormal ventricles are reviewed. Results . Normal ventricles possess an inlet, an apical trabecular component, and an outlet. This tripartite approach is also logical in the description of congenitally malformed ventricles. Rudimentary and incomplete ventricles lack one or more of its component parts, and are usually hypoplastic. The location and morphology of the rudimentary ventricles correlate with the disposition of the atrioventricular conduction system. Conclusions . Recognition of the ventricular components permits determination of ventricular morphology and guidelines for the location of the atrioventricular conduction axis.

Background . The concept of "one and a half ventricular repair" relates to situations where one ventricle is capable of pumping one half of the circulation while the other ventricle is deemed inadequate and requires off-loading by means of a shunt. The inadequate ventricle is usually assigned the role of pumping the pulmonary circulation. The majority of hearts potentially amenable to this repair will have one large ventricle associated with a smaller and more-or-less rudimentary ventricle. Methods . In this review, we focused on hearts in which the morphologically left ventricle will continue to support the systemic circulation. Results . Among the hearts with univentricular atrioventricular connections, a few cases of classic tricuspid atresia and cases of double-inlet left ventricle coexisting with concordant ventriculoarterial connections would be suitable for incorporating the right ventricle into the pulmonary circulation. This procedure may be feasible in some cases of straddling and overriding tricuspid valve. Hearts with pulmonary atresia and intact ventricular septum display a wide range of sizes of the right ventricular cavity. Although biventricular repair is an option for those with good-sized cavities, patients with hypoplastic right ventricles may be candidates for one and a half ventricular repair. Conclusions . For the lesions reviewed, and many others, one and a half ventricular repair can be an option.

Objectives. This study aimed to clarify the clinical anatomy of the pulmonary root. Background. Many descriptions of valvular anatomy have focused on the annulus, leading to varied interpretations of abnormal valves. Methods. Twenty-two heart specimens with isolated pulmonary valvular stenosis were examined to analyze the gross structure of the pulmonary root. For comparison, we examined a normal series of a similar age range together with nine adult hearts. Serial histologic sections were prepared from five specimens. Results. The normal pulmonary valve is enclosed in a proximal sleeve of free-standing right ventricular infundibulum supporting the fibroelastic walls of the pulmonary sinuses at the anatomic ventriculoarterial junction. The valvular leaflets are attached in semilunar fashion across this junction, delimiting the extent of the valvular sinuses. The stenotic valves were separated into dome-shaped valves, dysplastic valves and a third group of less typical cases. In the dome-shaped valves, which had a relatively circular origin of their leaflets, three raphes were tethered to the arterial wall at the sinutubular junction, producing a waistlike narrowing. The leaflets of the dysplastic valves were attached in a relatively normal semilunar fashion, but stenosis was caused by thickening of the leaflets at their free edges. Serial histologic sections through normal and abnormal valves failed to demonstrate any well defined fibrous “annulus” that could be of clinical relevance. Conclusions. Unlike the normal and the dysplastic valves, the dome-shaped valves have circular rather than semilunar lines of attachment of the valvular leaflets. Liberation of the fused zones of apposition of the leaflets within the dome is unlikely to restore such abnormal valves to normal structure, even if this procedure relieves the stenosis.

Anomalous origin of a coronary artery is occasionally associated with other congenital heart malformations. Presence of the anomalous artery can then complicate surgical repair. We report an unusually complex arrangement in a patient who died 16 hours following complete surgical repair despite appropriate management.

Ebstein's malformation involving both atrioventricular valves is a very rare entity. We report two cases in which the atrioventricular valves were also associated with multiple orifices. The first was an adult with known congenital heart disease. The true nature of the valvar malformation, associated with atrioventricular septal defect, was only discovered at autopsy. The second case was a neonatal heart specimen associated with hypoplastic left ventricle and aortic atresia. A review of the literature showed that Ebstein's malformation was rarely associated with atrioventricular septal defect. While accessory orifices were common in the left atrioventricular valve, they were rarely found in the right atrioventricular valve. Our cases, therefore, showed a very rare combination of seemingly disparate defects at the level of the atrioventricular junction.

We sought to analyze morphometric features of atrioventricular septal defect (AVSD) in autopsy specimens and to consider the developmental implications of obstruction in either ventricular outflow tract. Left ventricular outlet obstruction (LVO) is more prevalent in patients with Rastelli type A morphology. When tetralogy of Fallot (ToF) complicates this malformation, there is usually a free-floating superior bridging leaflet. The reasons for these associations are uncertain. In 133 hearts with AVSD and common atrioventricular (AV) valve orifice, we measured the degrees of horizontal and anterior deviation of the great arteries from the AV valve, the diameters of the ventricular outlets and the great arteries and the degree of deficiency of the ventricular septum. In Rastelli type A morphology, the great arteries were deviated more leftward than in type C morphology (p < 0.01). Type A hearts also had a relatively small aorta, with a long and narrow subaortic tract. The presence of obstruction in either ventricular outlet was associated with a more oblique arrangement of the great arteries, with the pulmonary trunk being more leftward than in hearts without LVO (p < 0.01). In combination with ToF, the aorta was dextroposed and the pulmonary trunk was located more posteriorly (p < 0.01). No heart with type A morphology showed ToF (p < 0.01). The geometric arrangement of the great arteries correlated significantly with obstruction in either ventricular outflow tract and with the Rastelli subtypes. Malrotation of the developing outlet septum may be an embryologic factor producing obstruction, with horizontal deviation of the outlets also influencing the morphology of the superior bridging leaflet

Atrial Fibers. 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 contribute 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.

Ein groser Teil der Patienten mit supravalvularer Aortenstenose zeigt pathologische Veranderungen der Aortenklappe selbst. Eine ausgepragte Redundanz der Klappensegel, hervorgerufen durch die verengte sinutubulare Leiste als Aufhangepunkt derselben, kann zu fruhzeitigen degenerativen Veranderungen der Klappensegel fuhren. Die sogenannte “supra”-valvulare Stenose beeintrachtigt also stets Struktur und Funktion der gesamten Aortenwurzel. Ein korrektiver chirurgischer Eingriff sollte diesem Rechnung tragen, indem die Leiste uber allen drei Sinus durchtrennt und adaquat erweitert wird.

Many of the controversies surrounding the description of ventricular septal defects arise from differences in the perspectives from which they are viewed. In this review, we analyse these defects as seen in cross-sectional echocardiographic images, correlating them with morphologic specimens. The classification we advocate, which now has a suitable pedigree, is a simple descriptive method distinguishing between perimembranous, muscular, and doubly committed types of defects. The approach is to categorise the defects as seen from the right ventricle, the usual port of access for surgeons. The term ‘perimembranous’ highlights the proximity of the atrioventricular conduction axis to the margin of the defects in which the remnant of the membranous septum forms a direct border. This system is applicable to all interventricular communications, no matter how malformed the heart may be in which they are enclosed.

Quantitative and qualitative cineangiographic analysis of the left ventricle (LV) was performed in 26 patients with isolated Ebstein's malformation, having a mean age of 23 +/- 17 years. Nine autopsied hearts with isolated Ebstein's malformation were submitted to morphologic and morphometric analysis. In 4 of the cases, it was possible to make a direct correlation between the angiographic data obtained during life and the autopsy findings. On the basis of the LV end-diastolic volume we identified 3 groups of patients: 7 with volume60 ml/m2, another 7 with volume between 60 and 80 ml/m2, and 12 with volume80 ml/m2. The LV ejection fraction was reduced in 2 patients with normal LV end-diastolic volume and in 6 with increased LV end-diastolic volume. The ratio of ventricular mass to LV end-diastolic volume was always adequate, but a reduction of the ventricular contractive performance (end-systolic pressure to end-systolic volume ratio3 mm Hg/ml/m2) was found only in patients with a dilated left ventricle. No correlation was demonstrated between the extent of the atrialized component of the right ventricle (mean value 67 +/- 31 cm2, range 13 to 133) and the LV dimensions. All but 2 patients showed a leftward diastolic displacement of the ventricular septum, but in only 1 did this produce an elongated shape of the left ventricle. Sixteen had anomalies of LV dynamics: 10 with hypokinesia (3 of the posterior wall, 4 of the apex, 1 of the inferior wall, 1 of the septum, and 1 global), 6 with dyskinesia (1 of the posterior wall, 2 of the apex, 1 of the posterior wall and apex, 1 of the superior part of the septum, and 1 of the anterior wall), and 8 with premature diastolic distension of the anterobasal wall. Morphometric analysis produced mean values for myocytes of 59 +/- 10%, for the interstitium of 21 +/- 4%, and for fibrous tissue of 20 +/- 9% (normal 4 +/- 1%). Five autopsied hearts had a prolapsing and/or dysplastic mitral valve.

The histological findings from a patient with Wolff-Parkinson-White syndrome (right superior paraseptal accessory pathway) who underwent successful radiofrequency ablation and had recurrence of tachycardia one month later in the absence of overt pre-excitation are reported. Histology revealed three small, oval to circular shaped, whitish, smooth areas on the right endocardial surface, the one being situated at the atrial free wall, and the other two being at the ventricular aspect. A very small hole was present in the interventricular component of the membranus septum. The accessory pathway band passed to either side of the small hole albeit disrupted by fibrous tissue in places. These findings indicate that multiple applications may cause penetration of the myocardium, and to achieve success, complete disruption of the pathway at some point along its course is required. Recurrence of retrograde accessory pathway conduction can be explained with the impedance mismatch hypothesis.

We examined the coronary arterial orifices in relation to the aortic valve to determine the range of normality in 23 normal hearts from autopsied adults. We determined the position of the zones of apposition between leaflets, the size of the leaflets, the number, position, and shape of the coronary arterial orifices, and their relation to the sinutubular junction. The aortic valve had three leaflets in all specimens, nearly equally spaced around the aorta. The left coronary artery arose within the left posterior aortic sinus (of Valsalva) in 16 (69%) specimens, above the sinutubular junction in five (22%), and at the level of the junction in two (9%). The distance of the left orifice from the zone of apposition between the left posterior and anterior aortic leaflets was between 13% and 61% of the width of the aortic sinus at the sinutubular junction. The right coronary artery arose within the anterior aortic sinus in 18 (78%) specimens, above the junction in three (13%), and at the level of the junction in two (9%). The distance of the orifice from the zone of apposition between the leaflets hinged from the anterior and right posterior aortic sinuses was between 5% and 62% of the width of the aortic sinus at the sinutubular junction. An accessory coronary orifice was found in the anterior aortic sinus in 17 (74%) specimens, whereas a third orifice in this sinus was found in five hearts. The coronary arterial orifices are usually located within the aortic sinuses below the sinutubular junction, but are rarely centrally located. Accessory coronary arterial orifices are found in the majority of the anterior aortic sinuses.

The concept of sequential analysis of congenitally malformed hearts is now widely accepted, although some aspects remain controversial. In this review, we analyse the evolution of the scgmental approach, showing how our own concepts of analysis have chaanged little since our initial description, heart dicrates the presence of the atrial, ventriclar, and arterial segments, Analysis depends upon recognizing the morphologic differences of the components within each segment, and then how these parts are joined together across the atrioventicular and ventriculo-arterial Junctions. The distinction of chambers and arterial trunks follows the principle of the morphologic method, namely that scructures be identified on the basis of their own intrinsic morphology, and not according to other features which themselves might be variable. Differentiation of junctional arrangements as opposed to segmental stucture resolves ongoing controversics such as the nature of “univentricular hearts”.Analysis in the fashion proposed shows that there is nothing intrinsically complicated with malformed hearts.

The fibrous skeleton of the heart has featured prominently in anatomical and surgical descriptions, although all its purported components are difficult to demonstrate. In descriptions of the skeleton, there have been repeated references to the presence of a tendon (or ligament) between the aortic and pulmonary roots. Such a tendon is rarely, if ever, discussed in the context of surgical procedures being carried out on the ventricular outflow tracts. Our study was undertaken, therefore, to investigate the existence and nature of such a tendon or ligament. Serial transverse sections were made through roots of aorta and pulmonary trunk in an intact fetal heart. In addition, ten normal adult hearts were dissected to display the components of the fibrous skeleton of the heart. No discrete fibrous or elastic structure could be detected in the tissue plane between the aortic sinuses and the subpulmonary muscular infundibulum, although a fascial strand was observed in one heart. Apart from this specimen, the space between the free-standing muscular subpulmonary infundibulum and the sinuses of aorta hearing the coronary arteries was occupied only by loose fibroareolar tissue. The initial presence of the ligament was described following studies of animal and macerated human hearts. Subsequently, it would seem its existence has been passed down through generations of morphologists and surgeons without its presence being reconfirmed. We have been unable to demonstrate any structure approximating to the initial illustrations.

Bachmann’s bundle (BB), also known as the interatrial bundle, is well recognized as a muscular bundle comprising of parallel aligned myocardial strands connecting the right and left atrial walls and is considered to be the main pathway of interatrial conduction.1 Disruption of the bundle’s structure causes interatrial conduction block (IAB),2 which is associated with development of various atrial tachyarrhythmias3,4 and with electromechanical dysfunction of the left atrium.5 Technological progress providing sophisticated mapping and imaging techniques in the past decade has increased our knowledge of specific anatomic structures and their role in development of both atrial brady- and tachyarrhythmias. This review outlines the current knowledge of the relation between anatomic and electrophysiological properties of BB and its possible role in initiation and perpetuation of atrial fibrillation (AF). In 1963, Thomas N. James described 3 pathways connecting the sinus node to the atrioventricular node (AVN), namely the anterior, medial, and posterior internodal pathways.6 Whether these conduction pathways were because of the presence of specialized conduction tissue or because of the anisotropic orientation of the muscle fibers remains controversial. Nevertheless, James described the anterior pathway as leaving the sinus node in anterior direction and giving off a secondary branch at the level of the superior vena cava to form BB.1 BB stretches subepicardially across the interatrial groove (septal raphe). It is at the interatrial groove that the BB can be identified as a discrete bundle (Figures 1 and 2) separated by fatty tissues from the infolded right atrial wall that is the limbus of the oval fossa. Notably, the bundle is not surrounded by a fibrous tissue sheath. Instead, the bundle is comprised of strands of atrial myocardium that are similarly aligned in parallel fashion. Its rightward and leftward extensions bifurcate to pass to either …

In children with structurally normal hearts, the mechanisms of arrhythmias are usually the same as in the adult patient. Some arrhythmias are particularly associated with young age and very rarely seen in adult patients. Arrhythmias in structural heart disease may be associated either with the underlying abnormality or result from surgical intervention. Chronic haemodynamic stress of congenital heart disease (CHD) might create an electrophysiological and anatomic substrate highly favourable for re-entrant arrhythmias. As a general rule, prescription of antiarrhythmic drugs requires a clear diagnosis with electrocardiographic documentation of a given arrhythmia. Risk-benefit analysis of drug therapy should be considered when facing an arrhythmia in a child. Prophylactic antiarrhythmic drug therapy is given only to protect the child from recurrent supraventricular tachycardia during this time span until the disease will eventually cease spontaneously. In the last decades, radiofrequency catheter ablation is progressively used as curative therapy for tachyarrhythmias in children and patients with or without CHD. Even in young children, procedures can be performed with high success rates and low complication rates as shown by several retrospective and prospective paediatric multi-centre studies. Three-dimensional mapping and non-fluoroscopic navigation techniques and enhanced catheter technology have further improved safety and efficacy even in CHD patients with complex arrhythmias. During last decades, cardiac devices (pacemakers and implantable cardiac defibrillator) have developed rapidly. The pacing generator size has diminished and the pacing leads have become progressively thinner. These developments have made application of cardiac pacing in children easier although no dedicated paediatric pacing systems exist.

Background The prevalence and clinical consequences of coronary arterial injury in a large series of patients undergoing radiofrequency ablation (RFA) of atrial fibrillation (AF) are unknown. Objective The purpose of this study was to describe the frequency and clinical consequences of coronary arterial injury in a large series of patients undergoing catheter ablation of AF and postablation atrial tachycardia. Methods The medical records of 5,709 consecutive patients undergoing RFA of AF were reviewed. Heart specimens were also dissected to analyze the course of the coronary arteries. Results Arterial injury occurred in 8 patients (0.14%). Three patients developed ventricular fibrillation (VF) due to occlusion of the distal or proximal circumflex (Cx) artery related to RFA in the distal coronary sinus (CS) or base of the LA appendage, respectively. Two VF patients underwent stenting. Five patients developed acute sinus node (SN) dysfunction. In 4/5 patients, the culprit site was subjacent to the SN artery (per computed tomography) coursing over the anterior LA (n = 3) or the septal RA (n = 1). Two patients required a permanent pacemaker. In the heart specimens, the SN artery, after its origin from the proximal Cx artery, coursed along the anterior LA. Also, the proximal Cx artery was found in the atrioventricular groove underneath the base of the LA appendage. Conclusion Clinically apparent injury to the coronary arteries during LA ablation for AF is rare. However, it may be associated with potentially life-threatening ventricular arrhythmias and acute SN dysfunction requiring permanent pacing. The culprit sites seem to be in the distal coronary sinus and the anterior LA, and correlate well with the course of the coronary arteries in pathologic specimens. Vigilance and low-power settings are important in minimizing the risk of arterial injury.

Double-chambered left ventricle is a rare congenital disorder in which the left ventricular cavity is subdivided into two cavities by an anomalous septum or muscle band. We describe a case of double-chambered left ventricle, most likely caused by the presence of excessive left ventricular bands, in an asymptomatic cat.

Aims We analysed the type and mechanism of supraventricular arrhythmias encountered in a series of symptomatic adults with atrial isomerism undergoing catheter ablation procedures. Methods and results The study population included consecutive adults with atrial isomerism who had previously undergone surgical repair or palliation of the associated anomalies. Patients underwent electrophysiological study for symptomatic arrhythmia in our institution between 2010 and 2012 using magnetic navigation in conjunction with CARTO RMT and three-dimensional (3D) image integration. Eight patients (five females) with a median age of 33 years [interquartile range (IQR) 24–39] were studied. Access to the cardiac chambers of interest was obtained retrogradely via the aorta using remotely navigated magnetic catheters in six patients. Radiofrequency ablation successfully targeted twin atrioventricular (AV) nodal reentrant tachycardia in two patients, atrial fibrillation (AF) in three, focal atrial tachycardia (AT) mainly originating in the left-sided atrium in four patients, and macro-reentrant AT dependent on a right-sided inferior isthmus in three patients. The median fluoroscopy time was 3.0 min (IQR 2–11). After a median follow-up of 10 months (IQR 6–21), five of the ablated patients are free from arrhythmia; two patients experienced episodes of self-terminated AF and AT, respectively, within one month post-ablation; the remaining patient had only non-sustained AT during the electrophysiological study and was managed medically. Conclusion Various supraventricular tachycardia mechanisms are possible in adults with heterotaxy syndrome, all potentially amenable to radiofrequency ablation. The use of remote magnetic navigation along with 3D mapping facilitated the procedures and resulted in a short radiation time.

We report on a patient with a significantly enlarged right heart caused by a rare right ventricle to right atrium fistula. Cardiac magnetic resonance revealed diagnosis and delineated detailed anatomy of the defect. The shunt was successfully closed with an implantation of Amplatzer Vascular Plug II. We discuss possible causes of this anomaly and its treatment.

Deep clefts are a cause of early failure of mitral valve repair, but it is not known whether clefts represent normal morphology, or whether they occur more frequently in mitral valve prolapse (MVP).Deep clefts were defined as indentations extending ≥ 50% of the depth of the mitral valve leaflet. Using trans-oesophageal echo (TOE), 3D zoom images were acquired of the mitral valve in 176 patients: 76 patients with MVP, 43 patients with alternative causes of mitral regurgitation (MR), and 57 controls. Three-dimensional TOE results were corroborated with findings made at surgery for a subset of patients who subsequently underwent mitral valve surgery. An assessment of the proportion of the valve that was prolapsing was documented, and correlated to the number of clefts. The relationship of clefts to the region of prolapse or flail was recorded. Three-dimensional TOE was 93% sensitive and 92% specific for detecting clefts. Clefts were documented in 84% of patients with MVP, but significantly less frequently in patients with alternative MR (16%; P0.001) and controls (12%, P0.001). Clefts always appear in prolapsing regions or framing them, and the number of clefts increased in patients with more extensive prolapse.Clefts are frequently seen in MVP, but are uncommon in patients without this diagnosis. They occur in greater numbers as a larger proportion of the valve prolapses. They may play an important role in the development of MVP.

The cardiac conduction tissues in the human heart comprise specialized myocytes that can be differentiated from working myocardium with routine histological staining. They are located in specific regions of the heart to form the sinus node and the atrioventricular (AV) node, which then extend into the AV bundle and bundle branches. Both cardiac nodes are sited in the atria with working atrial myocardium in between (so called internodal preferential pathways). Atrial myocardium is separated from ventricular myocardium by fibrofatty tissues at the AV junction and rings. In the normal heart, the continuation of specialized myocytes from the AV node that forms the bundle of His, penetrating the central fibrous body, is the only muscular continuity between atrial and ventricular myocardium, allowing atrial impulses to be conveyed to the ventricles in an orderly fashion. In this chapter, we will deal with normal and pathological features of the conductive tissue of the heart.

Atrial fibrillation (AF) is the most prevalent arrhythmia in western countries and it is estimated that its prevalence will increase further over the coming decades. AF affects 1% of the general population and up to 17% of patients aged >84 years.1 Until recently, pharmacological therapy has been the only treatment, but its efficacy is limited in terms of maintenance of sinus rhythm and control of symptoms.2 Over the last decade catheter based ablation of AF has proved to be more efficacious in comparison to medical treatment,3 especially in the paroxysmal form. Moreover, the catheter ablation strategy has evolved considerably, leading to significant improvements in efficacy and reductions in the procedural complication rate. Initially, linear lesions were performed in the atria mimicking the surgical Maze procedure4 which, however, resulted in limited success and significant complications. Haissaguerre et al 5 and Chen et al 6 found that AF is most commonly initiated by a premature beat from the orifices of the pulmonary veins (PVs). As a result, the procedure initially targeted elimination of foci inside the triggering vein (the earliest PV electrogram that initiates tachycardia), but this strategy was not effective enough to prevent recurrences which originated from the same or other veins. Therefore, electrical disconnection of all four PVs from the atrium became the proposed treatment option. The antral (also called circumferential) isolation of the veins is the approach that is most frequently used nowadays,7 and in many cases cures the disease. As the atrium becomes more dilated and fibrotic, other structures in addition to PVs are increasingly being recognised as a possible source of AF initiation and/or are key in the perpetuation of AF. Typical locations of triggers and the micro-reentry circuit are one or more of the following atrial structures: left lateral ridge (LLR), left …

OBJECTIVE. MRI and CT have become the ideal methods for assessing the complex function of the conotruncal region, including the right ventricular outflow tract (RVOT). In this review, we focus on the role of CT and MRI to evaluate RVOT function in relation to developmental malformations. CONCLUSION. We discuss the role of imaging pertinent to electrophysiologic assessment for cardiac arrhythmias. The RVOT is an important ablation target for radiofrequency ablation of ventricular tachycardia. Architectural changes of the myocardial strands in the RVOT, scar, and fibrofatty tissue may play a role in the development of RVOT ventricular arrhythmias. With CT and MRI, some of these changes can be revealed.

BACKGROUND: Little attention has been paid to the architecture of the muscle fibres of the ventricular walls in congenitally malformed hearts. In this study the gross pattern of myocardial fibres in normal hearts was compared with that in cases of tetralogy of Fallot. METHODS AND RESULTS: After morphological examination nine specimens with tetralogy were dissected to study the ventricular myoarchitecture. Changes were found in the shape of the malformed ventricles. The ventricular walls were arranged in layers in all hearts. Superficial and deep layers were present in both ventricles, with the superficial layer showing a more oblique orientation in the specimens with tetralogy than in normal hearts. Modifications of muscle fibre that were related to the type of malformation were seen in the deep layer. A middle layer was present in the left ventricles of normal hearts and specimens with tetralogy: this showed a horizontal orientation in both groups. In contrast, a middle layer was found in the right ventricle only in specimens showing tetralogy. CONCLUSIONS: The malformed hearts showed modifications in ventricular shape, in the arrangement of muscle in the right ventricle, and in the overall myoarchitecture. These changes could well be the consequence of the same agent (or agents) that caused the structural defect.

OBJECTIVE: To assess the current value of necropsy in paediatric cardiology and cardiothoracic surgery and determine its potential impact on clinical practice. DESIGN AND SETTING: Descriptive study of all paediatric cardiac deaths occurring over four years in a tertiary referral centre. Data were obtained from reviewing the hospital files, available necropsy records and specimens, and audit reports. PATIENTS: Paediatric patients with congenital or acquired heart disease, who died of a cardiac cause between January 1992 and July 1995. Inclusion criteria were that the diagnosis of heart disease was made before death, and that patients were managed thereafter medically and/or surgically at the referral centre. The value of necropsy was assessed according to its contribution in establishing the cause of death (confirmed, clarified, precise cause of death uncertain) and the anatomy (simple confirmation or additional information provided). For cases not submitted to necropsy the clinical information relating to the cause of death was assessed and the case assigned as cause of death firm, uncertain, or unknown. RESULTS: One hundred and six deaths were identified (61 males, age at death: one day to 20 years). Seventy occurred early (a month or less) after surgery and were graded as postoperative deaths. The rest were considered to be either medical or late surgical deaths. Necropsy was performed in 59 (55.6%). The precise cause of death was confirmed in 33 (55.9%), clarified in 22 (37.3%), and remained uncertain in four (7.8%). Additional information regarding the anatomy was found in eight (13.6%) cases. In five cases (8.5%) the necropsy detected findings which, if known before death, would probably have improved outcome. For the patients dying without a necropsy, the cause of death remained uncertain in 10 (21.3%) and unknown in seven (14.9%). In 36% of cases, therefore, a firm cause of death that might have been provided by a necropsy was missing. CONCLUSION: In paediatric cardiology necropsy continues to provide clinically relevant information at a high level. It remains vital for ensuring quality of medical care, in instigating improvements in future management, and increasing understanding of congenital heart disease. The procedure should therefore be sought actively in all cases.

In this fourth part of our series of articles concerned with the surgical anatomy of ventricular septal defects (VSDs), we have analyzed the arrangements when both arterial trunks arise from the same ventricle. The essence of these anomalies is that the interventricular communication is an integral part of the circulation. Unless the surgeon constructs an alternative route of exit, closure of this defect would isolate one of the ventricles. The usual surgical approach, therefore, is to patch the hole between the ventricles into one or other of the subarterial outflow tracts. This means that all the components of the ventricular outflow tracts are of potential surgical importance. In hearts with double outlet right ventricle, the VSD can be categorized as being subaortic, subpulmonary, doubly committed, or non-committed. It is also important to determine whether its anatomical borders, as seen from the right ventricle, are in part fibrous or exclusively muscular, so as to establish the location of the atrioventricular conduction axis. It is possible, according to the nature of these borders, to place the defects into one of three groups, perimenbranous, muscular, or doubly committed and juxta-arterial. The size of the defect is another important surgical consideration. Double outlet left ventricle is a significantly more rare malformation, but the rules for determining the disposition of the conducting tissues are the same.

Clinical Summary An incidental heart murmur in a 24-year-old woman led to discovery of an atrial septal defect with an apparent partition on echocardiogram. Transesophageal echocardiography and magnetic resonance imaging showed left pulmonary venous drainage into the left atrium (LA) and right pulmonary venous drainage into a midline atrial chamber that communicated with the right atrium (RA) but was completely partitioned from the LA (Figures 1 and 2, A). There were no other cardiac anomalies or visceral malformations. Cardiac catheterization confirmed absence of an interatrial communication and normal pulmonary artery pressure. There was a step up in oxygen saturation in the mid RA (94%) from the superior vena cava and high RA (78%). The main pulmonary artery saturation was 92%, whereas the right upper and lower pulmonary veins accessed through the RA into the midline chamber were 98% saturated. The left pulmonary venous drainage into the LA was visualized on the levo phase of the left pulmonary angiogram (Figure 2, B). During the operation, the heart appeared normal externally. Right atriotomy showed a midline atrial chamber, formed by a right-sided incomplete partition and intact left-sided atrial septum, into which opened the orifices of the right upper and lower pulmonary veins. The free margin of the partition was suspended from the septal aspect of the atrioventricular junction and allowed venous return from the right pulmonary veins to flow to the tricuspid valve orifice. The atrial septum and the partition were excised, and the resulting common atrial chamber was reseptated with autologous pericardial patch to allow all pulmonary venous return to be directed into the LA. The eustachian valve and the valve of the coronary sinus were in the anatomically normal position. The patient recovered uneventfully and remains symptom free 7 years after the operation. Postoperative echocardiography confirmed drainage of all pulmonary veins into the LA.

Aims Despite recognition that understanding gross anatomy of the right atrium is important in the era of invasive electrophysiology, areas such as the right atrial appendage (RAA) wall or the vestibule are not fully appreciated. The aim of this study was to conduct an anatomical assessment focusing on these structures to gain further insights into electrophysiological procedures. Methods Forty-four normal human hearts were examined macro- and microscopically. Results Inside the RAA, two prominent muscle bundles; the crista terminalis (CT) and the sagittal bundle (SB) were identified. The medial wall at which the CT originated from and its surrounding area was the thickest part adjacent anteriorly to the thin aortic mound, suggesting non-uniform wall thickness of this area. Histological sections revealed that myocardial strands of the SB connected the CT and RAA tip, implying preferential anterior conduction of the sinus impulse. The vestibule had a thin myocardium with extensive fat covering along the epicardial side of the tricuspid annulus. The proximal portion of the right coronary artery (RCA) was relatively distant from the annulus, followed by gradual shortening of the distance from the endocardium to the RCA, which led to a very close relationship (

This chapter gives the normal and pathologic morphology of the conduction system and relates it to important clinical arrhythmias. Abnormalities of the myocardium and the arterial supply of the conduction system, particularly those related to repair of congenital cardiac defects, are also discussed. The ways in which these morphologies are important to catheter ablation are well described.

We conclude, therefore, that description and analysis of visceral heterotaxy need to include considerations of the bodily organs as well as attention to cardiac structure. It must then be recognized that important differences exist between the groupings made on the basis of splenic status and morphology of the appendages. It is up to the individual investigator, based on the specific topic to be studied, to choose between the utilities of these different approaches.

To evaluate the use of three-dimensional (3D) echocardiography in the diagnosis of congenital heart defects, we studied 238 patients aged 3 days to 19 years (mean 4.3 years) with normal hearts (n=13) or a variety of congenital heart defects (n=225). Three different modalities of data acquisition suitable for 3D reconstruction were applied. For parallel scanning, the transducer is held in a 6-cm long scan frame and then moved over the thorax, or in the subcostal position, by a stepper motor using 0.5-mm steps with acquisition of perpendicular parallel images of the heart. For rotational scanning, the transducer is rotated at sectors of 2 degrees over a span of 180 degrees. For fan-like scanning, the transducer is moved in an arc 45 degrees each way from its vertical axis. Movement of the transducer is computer-controlled and performed with electrocardiographic and respiratory gating. Between 80 and 120 slices of the heart are thus obtained, which form the 3D dataset. This dataset can then be ¿sectioned¿ in any desired plane, thus permitting generation of views simulating intraoperative perspectives. Ventricular septal defects and atrioventricular valves can be displayed as viewed via the atrium. Muscular ventricular septal defects can be viewed as seen through a ventriculotomy. Obstruction in the left ventricular outflow tract can be viewed as via an aortotomy, and so on. We concluded that this new imaging modality has a vast potential and may facilitate planning of intracardiac surgery.