Conduction system defects in three perinatal patients with arrhythmia

The cardiac conduction systems of three patients who died in the perinatal period were studied histologically. Rhythm disturbances were observed in these patients immediately before death. The sinus node was notably hypoplastic without increase in fibrous content in all cases. The atrioventricular node was smaller than expected in all, and the entire atrioventricular conduction axis was small in two cases. This study supports the need for a detailed examination of the cardiac conduction system so as to provide a better understanding of the clinicoanatomical relation in the context of fatal perinatal arrhythmias.

Double-inlet ventricle: morphologic analysis and surgical implications in 32 cases

We analyzed, using a sequential segmental approach, 32 cases of double-inlet ventricle to assess the feasibility of surgical "correction" by either ventricular septation or a modified Fontan procedure. Twenty-two hearts had two atrioventricular valves, connected to a left ventricle in 19, a right ventricle in two, and a solitary indeterminate ventricle in one. Septation was possible in only 13. In contrast, the Fontan procedure seemed feasible in 20. The remaining 10 specimens had double inlet via a common valve to the left ventricle in two, the right ventricle in six, and an indeterminate ventricle in two. Seven of these had right atrial isomerism. Ventricular septation was not considered a possibility in these hearts. The Fontan procedure combined with atrial septation was a possibility in seven cases. From the morphologic stance, although the modified Fontan procedure seemed suitable in most cases, a significant number of hearts with two atrioventricular valves were suitable for ventricular septation.

The surgical significance of the atrial branches of the coronary arteries

The great number of open heart operations now performed via the right atrium, makes knowledge of the arrangement of the atrial arteries, particularly the sinus node artery, every important for the surgeon. Although studied by anatomists, little attention has been paid to the surgical significance of these arteries. We have therefore examined the distribution of the right atrial arteries and the course of the sinus node artery in 50 normal adult hearts by classic dissection following, in 30 cases, postmortem angiographic studies. Two major arteries of the right atrium were found to be nearly constant. The anterior artery was present in 96% of the cases and supplied the sinus node artery in 32 cases. Of most surgical significance was the lateral artery found in 90% of the cases. This lateral artery was the principal artery to the free atrial wall and in one case gave rise to the sinus node artery. The well-established preponderance of origin of the sinus node artery from the right coronary system (66%) as opposed to the left (30%) was confirmed. Infrequently, a double supply (4%) was seen. Variability was found in the course of the nodal artery relative to the cavoatrial junction - precaval (58%), retrocaval (36%) or encircling (6%).

Effects of high but nontoxic dietary manganese and iron on their metabolism by calves

Sixteen male Holstein calves were fed one of four diets for 18 days in an experiment consisting of 0 and 1000 ppm supplemental manganese and 0 and 1000 ppm added iron as manganese carbonate and ferrous carbonate. The control diet contained 55 ppm manganese and 220 ppm iron. All calves were dosed orally 48 h prior to sacrifice with 500 muCi of manganese-54. Small intestinal iron was less in calves fed a high manganese diet, a possible interaction of these two elements at the absorption site. Feeding a high manganese diet tended to decrease iron (total) concentrations in liver and pancreas. When the high manganese diet was supplemented with additional iron, antagonistic effects of manganese on iron were eliminated. Neither iron nor manganese concentrations in tissues were affected by an increase of dietary iron. Manganese-54 content of tissue was reduced by the high manganese diet but was not affected by dietary iron. Total manganese and iron in feces fairly closely reflected dietary intake of each element with no evidence of interaction. Calves fed the high iron diet excreted less manganese-54 in their feces over 2 days. Total iron in blood serum was not affected significantly by the dietary treatments.

Atrioventricular septal defect with intact atrial and ventricular septal structures

A heart with an atrioventricular septal defect is characterized by absence of the atrioventricular muscular and membranous septa, a common atrioventricular junction, an unwedged position of the aortic valve annulus and disproportionate inlet--outlet dimensions of the ventricular septum. The clinical and post-mortem findings are described of a case which had intact atrial and ventricular septa but had all the other anatomical hallmarks of atrioventricular septal defect. The problems in clinical diagnosis may be overcome by cross-sectional echocardiography.

The surgical anatomy of hearts with no direct communication between the right atrium and the ventricular mass--so-called tricuspid atresia

Seventy-six hearts were studied having no direct communication between the right atrium and the ventricular mass. The different cardiac chamber combinations producing so-called "tricuspid atresia" were considered. The nature of the atrioventricular valve atresia, the morphology of the ventricular mass, the size and position of the interventricular communication, the ventriculoarterial connection, and the presence of subarterial outflow tract obstruction were all analyzed. The majority of cases were of the "classical" type, i.e., absent right atrioventricular connection with the left atrium connected to the left ventricle. In another group there was absence of the right atrioventricular connection but the left atrium drained into the morphologically right ventricle, which was left-sided. In a third group both atrial chambers connected with the ventricular mass but some structure, an imperforate valve or muscular partition, completely blocked the flow pathway through the right side of the heart. All the hearts described are candidates for the Fontan procedure with either an atrioventricular or an atriopulmonary conduit. The surgical options would not be affected by the observed variability at the atrioventricular junction but would be dictated by the feasibility of incorporating the subpulmonary ventricle within the pulmonary circulation.

Endocardial fibroelastosis and hypoplasia of the left ventricle in neonates without significant aortic stenosis

Endocardial fibroelastosis in neonates with hypoplasia of the left ventricle is usually associated with severe aortic stenosis or atresia. In this study three hearts were examined, in which severe hypoplasia of the left ventricular cavity with myocardial hypertrophy and endocardial fibroelastosis were associated with small but non-stenotic subaortic outflow tracts and aortic valves. These features were contrasted with those of neonatal left heart hypoplasia in aortic stenosis and atresia. The index cases were examples of the very rare contracted form of endocardial fibroelastosis.

Malalignment of the interventricular septum with atrioventricular septal defect: its implications concerning conduction tissue disposition

Malalignment of the interatrial and interventricular septal structures is rarely seen associated with atrioventricular septal defects. Such malalignment gives rise to an anomalous disposition of the conduction tissue specifically in regard to the siting of the atrioventricular node. Recognition of this abnormality prior to (or at) surgery is important if post-operative rhythm problems are to be avoided.

Anatomical basis of cross sectional echocardiography

Ten hearts were cut in planes to simulate echocardiographic cuts which may be taken to visualise the anatomy of the cardiac chambers and great arteries. The various myocardial wall segments were named from these sections by referring to their position in the reconstituted heart. The sections were studied in their correct anatomical position. In this way they provide a reference for appropriate orientation of echocardiographic images.

Double-inlet left ventricle with rudimentary right ventricle and ventriculoarterial concordance

Seven hearts were studied that had in common the segmental combination of double-inlet left ventricle, rudimetary right ventricle and ventriculoarterial concordance. The prototype of these hearts has been described as the "Holmes heart" or "single ventricle type A1." Five of the hearts had 2 atrio-ventricular valves; in 1 of these the right valve was minimally straddling. The other 2 had a common valve. In 6 of the hearts the rudimentary right ventricle was obliquely situated on the anterior surface of the dominant left ventricle. The trabecular component was anterior and right-sided with the outlet components and pulmonary trunk in left-sided position. In the final case, both trabecular and outlet components of the rudimentary right ventricle were left-sided. Conduction tissue studies were performed in 2 hearts. In 1, the connecting atrioventricular node and bundle were in anomalous anterolateral position, as expected in double-inlet left ventricle. In the other, a ring-like, posterior, nonbranching bundle connected the regular node in the atrial septum to the branching bundle positioned on the anterior interventricular septum. The anatomic findings are related to the likely modes of presentation and differential diagnosis while the conduction tissue findings are discussed in the light of options for surgical repair. Thus, the term "single ventricle" is best avoided when describing hearts that unequivocally possess 2 ventricular chambers.

Aneurysm of the coronary sinus

Two patients, an adult and a baby, with an aneurysm of the coronary sinus are described. This unusual anomaly was detected in the baby during angiographic investigations for congenital heart disease. The aneurysm was an unexpected postmortem finding in the adult. Although the adult died suddenly, there was no evidence that this could be linked to the presence of the aneurysm.

Interrupted aortic arch--anatomical features of surgical significance

Analysis of 26 autopsy specimens with interruption of the aortic arch has led to a clearer understanding of the vital importance of associated cardiovascular abnormalities. In all cases there was an associated patent ductus arteriosus "supporting" the distal systemic circulation. "Proximal" septal defects, 22 ventricular septal defects and 3 aorto-pulmonary windows, were found in all but one specimen. The infundibular component of the ventricular septum was displaced posteriorly and leftward in 9 hearts resulting in significant left ventricular outflow obstruction in 8. In one specimen the infundibular septum was displaced anteriorly giving the effect of a "Fallot type" obstruction to the right ventricular outflow tract. Abnormal ventriculo-arterial connections were found in 7 hearts; 2 with discordant connection, 2 with double outlet, and 3 with single outlet of the heart. In 6 specimens there was an aberrant origin of the right subclavian from the distal aorta passing behind the esophagus to the right side. Various other arterial abnormalities were identified including a truncus arteriosus with separate but "transposed" origins of the pulmonary arteries. In short, in these hearts there were no examples of the rare situation where aortic arch interruption exists in isolation. This study therefore makes it very clear that a detailed understanding of associated anatomical abnormalities must accompany any attempt at surgical correction. Certainly in many of these cases management of the associated lesion will present more of a challenge than the difficult problem of dealing with the interrupted arch itself.

The surgical anatomy of the conduction tissues

On the basis of our collective experience we have reviewed the disposition of the cardiac conduction tissues as they might be observed by the surgeon in both normal and abnormal hearts. The sinus node lies subepicardially in the terminal sulcus; because of its variable blood supply the entire superior cavoatrial junction is a potential danger area. There are no morphologically discrete tracts extending through the atrial tissues between sinus and atrioventricular nodes. The atrioventricular node, the atrial extent of the atrioventricular conduction axis, is contained exclusively within the triangle of Koch. The axis penetrates through the central fibrous body and branches on the muscular ventricular septum immediately beneath the interventricular component of the membranous septum. The landmarks to these structures are described as they might be seen through the right atrium, left atrium, and aorta. Consideration is then given to the surgical anatomy of the abnormal muscular atrioventricular connections that underscore the ventricular pre-excitation syndromes. Finally, rules are developed whereby the disposition of the conduction tissues can be predicted with accuracy in congenitally malformed hearts, in the settings of both normal and abnormal chamber connections. The most important variables in this respect are alignment between the atrial and ventricular septal structures and the pattern of ventricular architecture present.

Late sudden death after repair of tetralogy of Fallot: a clinicopathologic study

Retrospective analysis was performed to determine the likely cause of death in six patients who died suddenly 1-9 years after repair of tetralogy of Fallot. The integrity of the atrioventricular conduction system and myocardium was examined in three hearts at necropsy. Two of three patients who complained of palpitation or syncope had frequent premature ventricular complexes on routine ECGs. All the patients had complete right bundle branch block and one had left-axis deviation after repair. Postoperative cardiac catheterization (four patients) showed no residual ventricular septal defects, but right ventricular pressure was elevated in all. At necropsy, the atrioventricular conduction tissue was related to the margin of perimembranous ventricular septal defect in two patients, but was well posterior in one patient with an infundibular muscular defect. Histologic examination showed that in all cases the atrioventricular node, atrioventricular bundle and left bundle branch were undamaged. There was, however, extensive fibrosis of the right ventricular myocardium in the ventriculotomy site (three patients), septum (one patient) and outflow tract (one patient). These clinical and necropsy findings suggest that ventricular arrhythmia rather than atrioventricular block was responsible for sudden death in these patients after repair of tetralogy of Fallot.

Aortopulmonary septal defect coexisting with ventricular septal defect and pulmonary atresia

Three patients are described in whom an aortopulmonary septal defect (aortopulmonary window) coexisted with a ventricular septal defect and pulmonary atresia. One patient had mild and another, moderate aortic regurgitation. In addition, one patient had a sinus of Valsalva aortic aneurysm, while another had a single coronary artery arising from the pulmonary trunk. One patient underwent surgical correction in infancy; the other two, in early adult life. In all three patients, surgical correction involved closure of the aortopulmonary window, closure of the ventricular septal defect, and placement of a valved conduit between the right ventricle and the distal pulmonary trunk. One patient died 3 weeks postoperatively due to secondary hemorrhage where the conduit had been sutured to the right ventricle. The other two patients are alive and well 3 1/2 years and 6 months after surgery, respectively. The presence of aortopulmonary window permits normal development of the pulmonary arteries in the presence of the coexisting pulmonary atresia; in the three patients described, the absence of pulmonary vascular disease made total surgical repair feasible for this combination of defects.

Absent left atrioventricular connection with right atrium connected to morphologically left ventricular chamber, rudimentary right ventricular chamber, and ventriculoarterial discordance. Problem of mitral versus tricuspid atresia

Four cases of absent left atrioventricular connection are reported. The observations from these cases have been used to emphasise problems concerning the use of the confusing terms "tricuspid" and "mitral" atresia to describe such hearts. One of the four cases represents a very uncommon condition since the rudimentary chamber was contralateral to the side of the absent emphasis given to the surgical implications of these anomalies.

Straddling atrioventricular valve with absent atrioventricular connection. Report of 10 cases

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Left-sided obstructive lesions in atrioventricular septal defects: an anatomic study

Actual and potential factors that create an obstruction to the flow within the systemic side of the heart have been analyzed in 114 specimens with atrioventricular septal defects. Hearts with separate right and left atrioventricular orifices and with common atrioventricular orifice were included. Potential inlet obstruction was due to tethering of the "cleft" of the left atrioventricular valve to the septum in 17.5%, incomplete "cleft" in 8%, and deformed valve leaflets in 70% of cases. Potential factors predisposing to left ventricular outflow tract obstruction were seen in 70% of cases, 21% being due to abnormal position of the papillary muscle and the remainder due to intrinsic hypoplasia of the outflow tract. Anatomic factors producing unequivocal obstruction were seen in 29% of cases. Twenty-two percent had obstructions at the inlet level, of which 13% were due to malformations of the left atrioventricular valve or the left component of a common valve. The other 9% had overall inlet obstruction due to severe hypoplasia of the left ventricle itself. Unequivocal outlet obstruction was observed in 7% of cases, 5% due to abnormal disposition of papillary muscles in the outflow tract and 2% to aneurysm of the interventricular septal remnant. Although anatomic obstruction occurs in the minority of cases (29%), this report shows that potential obstruction must be taken into account when considering surgical repairs.

Conduction tissue changes associated with enlarged membranous septum--a cause of sudden death?

We have studied four hearts in which enlargement of the ventricular membranous septum was associated with histological abnormalities of the atrioventricular conduction tissues. Two of the cases showed unusually formed penetrating and non-branching main atrioventricular bundles. These two cases plus one other also showed right-sided penetrating and main atrioventricular bundles. In addition these three cases all showed extensive fibre loss affecting the origin of the left bundle, which in one heart was further accompanied by fibre loss in the main bundle. The conduction tissue damage in the fourth case, though more extensive, was not as clearly related to the enlarged membranous septum since the heart in this case was also enlarged and dilated (congestive cardiomyopathy). Our findings, while obviously not conclusive, suggest that conduction changes in the presence of an enlarged membranous septum could be added to the list of causes of sudden cardiac death. They certainly indicate that when an enlarged membranous septum is found in cases of sudden death, histological study of the conduction system is desirable.

The internodal atrial myocardium

The anatomical substrates of internodal conduction have long been a contentious topic. Debated first by the German Pathological Society in 1910, the consensus of established opinion for over half a century was that conduction between sinus and atrioventricular nodes occurred through plain myocardium. This was a conclusion supported by Truex in 1961. Despite his restatement of this fact in 1976, it has become fashionable to describe internodal conduction as being mediated by specialized internodal pathways. To reinvestigate this problem we studied 22 human fetal and 32 human infant hearts. In each case it was possible to cut the atrial tissues as a single block of tissue and to examine serial sections through the internodal myocardium. The sinus node, atrioventricular node, and segments of atrioventricular ring specialized tissue were recognized as specialized tissue using the light microscope in each heart. In contrast, there was nothing "special" about the myocardium between the nodes, nor was it possible to recognize tracts on the basis of either histological appearance or cellular architecture. It is concluded that, from the standpoint of light microscopy, there is no evidence whatsoever to support the purported concept of specialized anatomical substrates for internodal conduction.

Surgical anatomy of double-outlet right ventricle with situs solitus and atrioventricular concordance

Sixty-three hearts with situs solitus, concordant atrioventricular connection, and more than half of both great arteries connected to the right ventricle have been studied to delineate their surgically important features. Specifically noted were the relationship of the arterial valves to each other and the type and position of the ventricular septal defect with special reference to the conduction tissue location. Infundibular morphology was ascertained and other congenital abnormalities were recorded. An estimate was made of the surgical options available given the various anatomic abnormalities present. The aorta was most commonly in the right posterior position but could be found anywhere in the arc extending to left anterior position. The septal defects were most frequently in subaortic position (34/65) and were usually of perimembranous type (45/65). Three hearts had two defects each and one heart had an intact ventricular septum. Identifying the type of defect was helpful in locating the conduction tissues. In addition, there were numerous associated anomalies, including 19 hearts with coronary artery malformations. Retrospective analysis of the surgical options suggested that 36% of the hearts would not have been operable during life. Approximately another third could have been corrected by use of an intraventricular tunnel from the ventricular septal defect to the aorta, and the remaining third would have needed more complex procedures. In the final analysis it was concluded that hearts with the ventriculoarterial connection of double-outlet right ventricle, though so varied as to preclude "standardization," did permit anatomic analysis and description in clear and consistent terms.

Surgical anatomy of tetralogy of Fallot

On the basis of previous experience, we have analyzed the anatomy of a series of 53 hearts catalogued as having tetralogy of Fallot in the museum of the Children's Hospital of Pittsburgh. All hearts had a ventricular septal defect, aortic overriding, infundibular pulmonary obstruction, and right ventricular hypertrophy. None of the hearts had been operated upon during life. We paid particular attention to features of surgical importance. Thus the ventricular septal defect was found to be of variable form. It was perimembranous in 42 hearts. In 11 hearts it had entirely muscular rims and in the remaining heart it was roofed by the conjoined aortic and pulmonary valve rings (subarterial). From our previous histologic experience, it was evident that this varying morphology significantly affected the surgical anatomy of the atrioventricular conduction tissues. We endeavored to display this disposition as might be viewed by the surgeon. The degree of aortic override was variable, the aortic valve being connected by 15% to 95% to the right ventricle. In 17 hearts more than half the aortic valve was attached to right ventricular musculature. The nature of the infundibular obstruction also varied markedly. In all cases (except the one with absent infundibular septum) the infundibular septum was deviated in cephalad and anterior direction so as to produce obstruction. In the majority of hearts further anatomic structures also contributed to the obstruction. In some hearts there was hypertrophy of the infundibular septum, particularly at its junction with the trabecular septum. In others there was hypertrophy of the trabecula septomarginalis, and in many hearts there was hypertrophy of additional anterior infundibular trabeculations. The pulmonary valve was the narrowest point of the outflow tract in only six hearts, but in many of the others, it was abnormal. The results emphasize that while hearts may exhibit the classical features of tetralogy of Fallot, there is usually considerable individual variation in each of these features which is of major surgical significance.