Atrioventricular conduction system in univentricular heart of right ventricular type with right-sided rudimentary chamber.

The conduction tissue in a univentricular heart of the right ventricular type with a right-sided rudimentary chamber was studied. Both an anterior and conventional node were found, the anterior node being positioned in the atrial septum very close to the conventional node. Between the two nodes, a sling of conduction tissue passed through the annulus fibrosus but was not related to the trabecular septum. A non-branching bundle descended on to a free-running trabecula in the main ventricular chamber, the trabecular septum itself being devoid of conduction tissue. We believe it is likely that this trabecula represents the trabecula septomarginalis of the normal right ventricle. It has recently been suggested that during development the primordium of the trabecula septomarginalis is the structure which carries the conduction tissue from the atrioventricular node (whatever its position) to the trabecular septum. The present findings seem to support this.     

The conduction system in truncus arteriosus and its surgical significance. A study of five cases.

Atrioventricular block may occasionally occur after surgical correction of truncus arteriosus. We therefore studied the conduction system by means of serial sections in five cases of truncus (one after surgical intervention) to delineate the course of the conduction system and its relationship to the ventricular septal defect and the membranous septum. In general, the ventricular septal defect is in the anterior septum, confluent with the truncus, and the atrioventricular bundle is posterior and unrelated to the rim of the ventricular septal defect. In cases in which the ventricular septal defect is anterior and separated from the membranous septum by distinct muscle, the ventricular septal defect can be surgically closed without injury to the atrioventricular bundle. If the ventricular septal defect is related to the membranous septum, the atrioventricular bundle may be close to the ventricular septal defect and susceptible to surgical injury. If muscle separates the ventricular septal defect from the membranous septum, the branching bundle is close to the ventricular septal defect and also is susceptible to surgical injury. In one operated case there was partial dissolution of the left bundle branch, and the right bundle branch was involved in surgical closure of the defect. In summary, in truncus the conduction system varies in its course and is related to the location of the ventricular septal defect and its relationship to the membranous septum. The ventricular septal defect may be close to or related to the membranous septum, and the atrioventricular bundle and the beginning of the bundle branches may be vulnerable to surgical injury.     

A modification of staged septation for univentricular atrioventricular connection.

A case is reported in which is described a modification of staged septation for univentricular atrioventricular connection with double-inlet left ventricle and left-sided rudimentary outlet chamber beneath the aorta. This modification diminishes the risk of atrioventricular conduction disturbances by gluing the perforated septation patch on the myocardium in the area overlying the central conduction system. Fixation of the patch was facilitated by exact fitting of the patch in this area, by ample contact of the patch and the myocardium in this area, and by immobilization of the patch because of equal pressures on both sides because of the perforation of the patch. In addition, this modification facilitates evenly drawing in of the ventricular free wall because already, in the first stage, the complete circumference of the patch is fixed, defining the maximal contribution of prosthetic material to the newly created septum.     

The conducting tissues in primitive ventricle with outlet chamber. Two different possibilities

The conducting tissues have been studied in two cases of primitive ventricle with outlet chamber. In one case the outlet chamber was to the right and in the other, to the left. In both cases there was an anterior node related to the anterior part of the right atrioventricular anulus. In the specimen with a left-sided outlet chamber (l-loop), the bundle passed through the atrioventricular-semilunar fibrous continuity and was intimately related to the posterior artery. Such a relation was absent in the specimen with a right-sided outlet chamber (d-loop), wherein the bundle directly descended on the posterior part of the septum between the main and outlet chambers. The septum is not considered to be the true ventricular septum but rather a hypertrophied trabecula septomarginalis.     

Surgical management of univentricular heart with subaortic obstruction

In children with a univentricular heart and a rudimentary subaortic chamber, surgical relief of subaortic obstruction caused by a restrictive bulboventricular foramen is associated with high morbidity and mortality. A 6-year-old child with a univentricular heart of the left ventricular type, a rudimentary subaortic chamber, and atresia of the left-sided atrioventricular valve had pulmonary artery banding in infancy. Severe subaortic obstruction subsequently developed. At operation, the pulmonary artery was transected and the stump was anastomosed directly to the posterior aspect of the ascending aorta, diverting left ventricular blood into the aorta through the pulmonary valve. The distal pulmonary artery was anastomosed side-to-side to the ascending aorta to provide pulmonary blood flow. Cardiac catheterization fifteen months after the operation demonstrated an excellent hemodynamic result. When the pulmonary artery is adequate in size, a bypass operation by way of an anastomosis between the ascending aorta and the pulmonary artery is a relatively safe and effective means of relieving the ventricular outflow obstruction caused by a restrictive bulboventricular foramen.     

Morphology of the posterior junctional area in atrioventricular septal defects.

The location and size of the coronary sinus in hearts with atrioventricular septal defect were investigated in relation to the known disposition of the atrioventricular conduction axis. We examined the morphology in 40 hearts and supplemented this series with two other hearts that had been serially sectioned previously. The coronary sinus received drainage from a persistent left superior caval vein in 5 hearts. Six cases of 40 had malalignment of the septal structures relative to the crux of the heart. In these, the conduction axis was anticipated to course in the position where the inlet ventricular septum met the atrioventricular junction. The coronary sinus terminated in the left atrium in 4 hearts: 2 in the morphological series and 2 that were sectioned for histological studies. The sectioned hearts showed the atrioventricular conduction axis in the usual position for the defect, unrelated to the coronary sinus. The principle that the node and penetrating bundle are located at the intersection of the ventricular septum with the atrioventricular junction holds good despite the variability of the coronary sinus.     

The anatomy of the septal perforating arteries in normal and congenitally malformed hearts

BACKGROUND: Many cardiac operations involve incisions and sutures on or near the ventricular septum. These jeopardize the septal perforating arteries. Our aim was to provide guidelines for the surgeon to predict the site of these vessels. METHODS AND RESULTS: We dissected 50 hearts. In 16 of these we also conducted histologic examination of the area of the septum containing the atrioventricular node, the penetrating bundle (of His), and the branching atrioventricular bundle to elucidate the source of the vascular supply to these structures. The major perforating septal arteries arise from the superior interventricular artery or, in hearts with a rudimentary right ventricle, from the superior delimiting artery. The first is usually the largest. The location of this artery can be predicted relative to the position of the medial papillary muscle. In abnormal hearts, holes within the ventricular septum in the presence of a well-developed muscular outlet septum were found to deviate the path of the septal perforating arteries in a predictable manner. The triangular area bordered by the margin of the ventricular septal defect, the muscular outlet septum, and the medial papillary muscle is free of major perforating arteries. The histologic studies showed that the conduction tissues at the base of the ventricles tend to receive their blood supply from arteries arising from the inferior interventricular artery, except in double-inlet left ventricle, in which the arterial supply is from the right-sided delimiting artery. CONCLUSION: The location of the first superior septal perforating artery is predictable in many cases. Its course leaves a triangular area on the muscular ventricular septum that is free of major arteries.     

Surgical implications of juxtaposition of the atrial appendages. A review of forty-nine autopsied hearts

We studied 49 hearts with juxtaposition of the atrial appendages, concentrating on the associated malformations and features of operative importance. Left juxtaposition was found in 42 cases (86%) and right juxtaposition in seven cases (14%). In the group of hearts with right juxtaposition, a normal segmental arrangement was present in three cases, double inlet in two cases, and double-outlet right ventricle in the remaining two cases. Hearts with left juxtaposition had usual atrial arrangement with concordant atrioventricular connection, together with anomalous ventriculoarterial connection in 22 cases and univentricular atrioventricular connection in 19 cases. Only one specimen had a normal segmental arrangement. A partial form of left juxtaposition was present in 60% of the specimens. Hearts with left juxtaposition had a transverse orientation of the atrial septum, which was displaced posteriorly and inferiorly in the medial atrial wall, separated from the orifice of the juxtaposed appendage by a muscular band. A small right atrial chamber was noted in hearts with anomalous ventriculoarterial connection, creating the potential for anatomic difficulties during operation conducted within the atria. In two thirds of the cases with classic tricuspid atresia, the size of the orifice of the juxtaposed appendage was larger than the atrial septal defect, and an anastomosis of the appendage with the pulmonary trunk was morphologically feasible.     

Ventricular septation using two-patch technique for total inlet-trabecular septal defect

A 3-year-old girl underwent ventriclar septation using 2 patch technique. Echocardiography at birth revealed single left ventricle with pulmonary hypertension. Pulmonary artery banding was performed at the age of 1 month. Echocardiography at the age of 3 years showed total inlet-trabecular septal defect. Ventricular septation was performed through the right atrium. The tendon of Todaro and the coronary sinus were in normal positions. Almost all of the inlet septum and trabecular septum were deficit, although the posterior median ridge was present. It was considered that the atrio-ventricular node was shifted inferiorly and the conduction system ran down the inlet septum as in the case of atrioventricular septal defect, since this patient had concordant atrioventricular( AV) connection. It was difficult to form the septum using a single patch because of complicated anatomy. Thus we decided to divide the patch in order to make smooth surface avoiding conduction injury. One patch was used for the trabecular defect using running sutures and another patch was used for the inlet defect using pledgeted mattress sutures. Eventually both patches were sutured together to close the defect. Regular sinus rhythm resumed, although 2:1 AV block appeared temporally. The patient was discharged at postoperative day 30 without any complication.     

The conduction bundle at the atrioventricular junction. An anatomical study

The variability in the topographical anatomy of the conduction bundle at the site of the atrioventricular junction has been studied in four normal human hearts. The junctional area has been removed en bloc and serially sectioned. The conduction bundle and adjacent structures such as the posterior limb of the trabecula septomarginalis and the membranous septum have been reconstructed based on calculations from the histological sections. The study reveals marked variability particularly in the extent of the posterior limb of the trabecula septomarginalis. In one instance, the muscle was almost totally absent so that the branching bundle was located in a midline position and subendocardial both to the right and the left ventricular septal surface. In two hearts, the posterior limb of the trabecula septomarginalis had ramified so that only a small segment of the conduction bundle was covered by muscle. In the remaining case, a well-developed posterior limb of the trabecula septomarginalis completely covered the conduction axis thus accounting for the left-sided position of the bundle. The variability encountered may render the conduction bundle vulnerable to the tensile strain of the tricuspid valve apparatus, enhancing the natural process of wear and tear which may lead to disruption of conduction fibres and heart block, particularly in the elderly. Since the detailed topographical anatomy of the conduction bundle in the atrioventricular junctional area appears to be highly variable from one individual to another, meticulous inspection is mandatory once the area is manipulated at surgery.     

Transposition of the great arteries with ventricular septal defects. Surgical considerations concerning the Rastelli operation

We studied the anatomy of the ventricular septal defect in 20 heart specimens and eight operated patients with transposition of the great arteries regarding the feasibility of the Rastelli operation. They were divided into three groups. In Group I, comprising eight cases, creation of a left ventricle-aorta connection was not prevented by interposition of the atrioventricular valve tissue, and the ventricular septal defect was large or could be enlarged sufficiently. Thus, the Rastelli operation was feasible in all cases. In Group II, comprising 12 cases, interposition of the atrioventricular valves was not present, but the ventricular septal defect was inadequate in size for a good left ventricle-aorta connection. Small or even medium-sized ventricular septal defects were not enlargeable because of surrounding structures or inadequate septum for resection. In all cases, the ventricular septal defect was a tunnellike structure with two orifices; attempted enlargement would be more difficult at the left ventricular end (not obvious to the surgeon's view) than at the right one. The Rastelli operation was judged inadvisable in these cases. In Group III, comprising eight cases, the Rastelli operation was considered inadvisable because of interposition of atrioventricular valve tissue. The size of the ventricular septal defect and the presence of interposed atrioventricular valves can be diagnosed preoperatively. The presence of enough available space for resection, especially at the left ventricular end, should be determined preoperatively and/or intraoperatively in patients with medium-sized ventricular septal defects requiring enlargement. The anatomy of the ventricular septal defect may significantly alter the surgical approach for patients with transposition of the great arteries and ventricular septal defect.     

The Surgical Anatomy of Ventricular Septal Defects with Univentricular Atrioventricular Connection

Hearts that do not possess one-to-one connections at the segmental junctions almost always produce a unlventrlcular atrioventricular connection. One ventricle Is usually large and dominant and the other small, lacking one or two of its components. The ventricular septal deficiency forms part of the circulatory pathway. We take the stance that only hearts that possess a truly solitary ventricular chamber are univentricular. They cannot have a ventricular septal defect, and so are excluded from this study. This review, therefore, is concerned with the morphology of septal defects In hearts in which both atrioventricular junctions are connected exclusively to a dominant left or a dominant right ventricle, and those lacking one atrioventricular connection, where the remaining valve is connected to a dominant ventricle. This morphology in the absence of one atrioventricular connection can be modified when there Is Overriding of the solitary atrioventricular valve. The ventricular septal defects are analyzed and categorized for the various groups, and the position of the conduction axis is described for the well-recognized entities.     

Modification of the radial procedure in a patient with partial atrioventricular septal defect

We successfully cured atrial fibrillation while preserving internodal conduction in a patient with a partial atrioventricular septal defect. Because the anterior and middle internodal tracts are interrupted by the defect, the lower right atrial incision of either the maze or the radial procedure may interrupt the remaining posterior tract, resulting in internodal conduction block. We deleted the posterior septal incision from the radial procedure and replaced it with a right-side left atriotomy. The patient resumed normal sinus rhythm with significant contraction of the right and left atria. The preserved internodal pathway through the posterior interatrial septum was confirmed by electrophysiologic study.     

A case of successful surgical treatment of straddling tricuspid valve associated with dextrocardia and VSD

A case of straddling tricuspid valve associated with dextrocardia and VSD was presented. Closure of ventricular septal defect and tricuspid valve replacement were performed on this patient. Since the straddling septal leaflet of the tricuspid valve shared a posterior papillary muscle in the left ventricle with the posterior mitral leaflet, division of this papillary muscle was thought to induce papillary muscle dysfunction of both leaflet. Hence, the chordae of straddling tricuspid leaflet was detached from the shared papillary muscle and the ventricular septal defect was closed by a large pericardial patch. Because of peculiar anatomy of the conduction system in this situation, the junctional area of the inlet septum and tricuspid annulus was avoided from stitching in VSD closure. Suture through the tricuspid septal leaflet and pericardial patch for VSD were used for tricuspid valve replacement as well. The patient showed uneventful postoperative course without any conduction disturbance including the right bundle branch block.     

The conduction system in hearts with pulmonary atresia and intact ventricular septum

BACKGROUND: Although a regular course of the conduction system is anticipated in hearts with pulmonary atresia and intact ventricular septum (PAIVS), it has never been demonstrated anatomically. In view of one of the surgical options in repair being debulking of the right ventricular wall, it is important to establish the location of the major conduction pathways. METHODS: Four hearts belonging to fetuses aged 18, 20, 22, and 29 weeks were examined. Entire hearts were serially sectioned and step sections were stained. The sinus node and atrioventricular conduction bundles were identified and their locations described. RESULTS: The conduction system in hearts with PAIVS is similar to that in normal hearts, although there was a minor variation in one of them. This was a heart affected by Ebstein malformation of the tricuspid valve. In this case, the right bundle branch terminated abruptly soon after its origin. CONCLUSIONS: Confirmation of the regular course of the cardiac conduction system is important to the development of strategies for surgical repair of PAIVS.     

Late recovery of atrioventricular conduction after pacemaker implantation for complete heart block associated with surgery for congenital heart disease

OBJECTIVES: Pacemaker implantation is a standard recommendation for patients with persistent complete heart block following surgery for congenital heart disease. This study was performed to determine the incidence and clinical significance of late recovery of atrioventricular conduction following pacemaker implantation. METHODS: Between 1990 and 2001, 5662 open cardiac procedures for congenital heart defects were performed at our institution. The postoperative course of all patients with complete heart block in whom a permanent pacemaker was implanted was followed on a monthly basis, by either clinical or transtelephonic follow-up. RESULTS: A total of 72 patients with persistent postoperative complete heart block underwent pacemaker implantation. After insertion of the pacemaker, recovery of atrioventricular conduction was recognized in 7 of 72 patients (9.6%) at a median of 41 days (18-113 days) after the initial cardiac operation. These included 3 patients with ventricular septal defect, 2 with ventricular inversion or single ventricle, and 1 each with left ventricular outflow tract obstruction and atrioventricular septal defect. During a mean follow-up of 4.4 +/- 2.6 years, there was no late recurrence of heart block. Three patients had residual right bundle branch block and 1 had first-degree atrioventricular block. CONCLUSIONS: Atrioventricular conduction may return in a small but significant percentage of patients following pacemaker implantation for complete heart block associated with congenital heart surgery. When recovery of atrioventricular conduction occurs within the first months after surgery it appears reliable, which suggests that lifelong cardiac pacing may not be necessary in these individuals.     

Diastolic asynchrony and myocardial dysfunction in patients with univentricular heart after Fontan operation

Background

We aimed to assess the existence of myocardial dysfunction and intra-univentricular diastolic asynchrony in patients after Fontan operation.

Methods

Twenty patients after Fontan procedure and 30 age-matched controls were included in the study. The global function of the univentricular heart was analyzed by the Tei index. Regional myocardial velocities and strain of the univentricular heart including the rudimentary right ventricle (RV) were quantified by tissue Doppler imaging. Intra-univentricular or intra left ventricular (LV) diastolic delay was measured from the difference of diastolic intervals (time to peak early diastolic velocity), measured at LV lateral wall and the rudimental RV wall in patients, or LV lateral wall and the ventricular septum in controls.

Results

Compared to the control group, patients after Fontan operation had significantly elevated Tei index (0.24 ± 0.02 vs. 0.41 ± 0.1, p < 0.001). On the other hand, the regional myocardial velocities and strains of the univentricular heart including the rudimentary RV were significantly reduced (p < 0.001). Among patients, there was a significant correlation between the Tei index of the univentricular ventricle and rudimentary RV strain (r = ?0.66, p = 0.01). The heart rate-corrected intra-univentricular diastolic delay was significantly prolonged among patients when compared to the intra-LV diastolic delay in controls (0.01 ± 0.9 vs. 1 ± 1.1, p = 0.005).

Conclusions

Myocardial dysfunctions and intra-univentricular diastolic asynchrony of the univentricular heart in patients after Fontan procedure are evident. The rudimentary RV in patients after Fontan procedure plays an important role in the determination of the global function of the univentricular heart.     

Surgical anatomy of the infundibular septum in transposition of the great arteries with ventricular septal defect

Anatomic variation of the infundibular septum was studied in transposition of the great arteries with ventricular septal defect in 23 hearts and double-outlet right ventricle with anterior position of the aorta in two hearts. Anterior displacement of the infundibular septum (i.e., "false" Taussig-Bing heart) was associated with coarctation or interruption of the aortic arch in 88% of the cases, whereas posterior displacement resulted in subpulmonary narrowing in 100% of the cases. Anterior displacement makes intraventricular rerouting from the left ventricle to the aorta difficult because of a long oblique route. In addition, the right ventricular cavity becomes smaller after closure of the ventricular septal defect. Therefore, arterial switch accompanied with transatrial or transpulmonary closure of the defect without ventriculotomy is recommended. In hearts with posterior displacement of the infundibular septum, the anterosuperior rim of the defect is difficult to approach through the tricuspid valve, and the route from the left ventricle to the aorta is rather straight. Hence, the Rastelli procedure is preferable. In hearts without displacement of the infundibular septum, either arterial or atrial switch with transatrial closure of the ventricular septal defect is applicable.     

Further observations on the morphology of atrioventricular septal defects

Certain morphologic aspects of atrioventricular septal defects ("endocardial cushion defects," "atrioventricular canal malformations") remain controversial. It is still not clear which precise lesions should not be placed in this category. For example, is an "isolated" cleft of the mitral valve or a perimembranous inlet ventricular septal defect to be so described? It is also not fully accepted that the left atrioventricular valve in these lesions bears little resemblance to a morphologically mitral valve. We have investigated these problems by both observation and mensuration. We determined the junctional circumference of the left atrioventricular valve leaflets and the ventricular dimensions in 130 atrioventricular septal defects (95 with common valve orifice and 35 with separate right and left atrioventricular orifices); in 50 hearts with perimembranous ventricular septal defects (20 extending into the inlet septum and 30 with outlet or trabecular extensions); in seven hearts with isolated cleft of the mitral valve, and in 10 normal hearts. All specimens came from the cardiopathological collection of Children's Hospital of Pittsburgh. The measurements showed conclusively that the atrioventricular septal defects were all directly comparable irrespective of the detailed morphology of the atrioventricular valve or valves. The group of atrioventricular septal defects was totally discrete as compared with all the other specimens that had normal atrioventricular septation. The left atrioventricular valve in atrioventricular septal defects is basically a three-leaflet valve which differs from the normal mitral valve in terms of its leaflet, its chordal support, and the arrangement of its papillary muscle. Its only similarity with the normal mitral valve is that it resides in the morphologically left ventricle and guards the left atrioventricular junction.     

Myocardial distribution of retrograde flow through the coronary sinus of the excised normal canine heart

Myocardial distribution of the retrograde flow through the coronary sinus in the canine heart was evaluated by observing the corrosion casts of the myocardial vessels after coronary sinus injection of a low-viscosity resin, Mercox, a compound that passes through capillaries. The apex and the left ventricular free wall were well perfused at the microvascular level, even in the presence of complete left main coronary artery occlusion, whereas the right ventricular free wall was not perfused effectively at this level in any heart. Although there was considerable variation in the perfusion of the ventricular septum from heart to heart, the entire septum was not perfused in some of the hearts. We considered this poor perfusion of the septum to be due to the presence of well-developed thebesian veins in the septum. Retrograde coronary sinus perfusion of cardioplegic solution may be a valuable alternative to protect the left ventricular free wall, especially in cases of critical coronary artery stenosis or occlusion. However, antegrade perfusion should be used also, whenever possible, for adequate protection of the septum and the right ventricular free wall.