Conducting tissues in univentricular heart of right ventricular type with double or common inlet.

Four specimens of univentricular hearts of the right ventricular type, three with two atrioventricular valves and one with a common valve, have been examined histologically to identify the atrioventricular conduction system. Three of the specimens were initially thought to have only one chamber within the ventricular mass, a chamber which had a right ventricular trabecular pattern. On detailed examination and with removal of blocks of tissue for histologic study, a second, rudimentary chamber was found in the posterior ventricular wall. This chamber had a trabecular zone of the left ventricular type and was connected with the main chamber only via a small defect in the septum which separated the two chambers. In all four cases the connecting atrioventricular node was dound in normal relationship to atrial markers and the penetrating bundle descended onto the posterior wall of the main chamber. In three cases it ran along the crest of the septum between the main chamber and rudimentary chamber, in relation to the septal defect. In two cases left bundle branch tissue was identified running into the rudimentary chamber. This pattern of conducting system is different from that previously identified in other varieties of univentricular heart and again underlines the importance of intraoperative mapping of the conduction system during surgery of the univentricular heart.     

Shallow stitching close to the rim of the ventricular septal defect eliminates injury to the right bundle branch

BACKGROUND: Complete right bundle branch block carries a deleterious effect on the long-term outcome of patients who undergo surgical treatment of the perimembranous ventricular septal defect. We describe a novel suturing method to reduce the prevalence of complete right bundle branch block. METHODS: From March 1996 through December 2000, 48 consecutive patients with perimembranous ventricular septal defect underwent patch closure using shallow stitches placed close to the rim (group 1). The same number of patients was randomly selected from those who had previously undergone surgery using deep stitches placed distant from the rim (group 2). Postoperative electrocardiograms were reviewed to compare the prevalence of complete right bundle branch block between groups. A morphologic study of the conduction system was performed to identify the vulnerable segment of the right bundle branch where the surgical damage tended to occur. Additional analyses were made to determine whether younger age and right ventriculotomy increased the prevalence of complete right bundle branch block. RESULTS: The prevalence of complete right bundle branch block in group 1 (6.3%) was significantly (p < 0.0001) lower than in group 2 (43.8%). The result was consistent with the morphologic finding that stitches of group 2 tended to damage the right bundle branch and those of group 1 did not. The younger age and right ventriculotomy did not increase the prevalence of complete right bundle branch block. CONCLUSIONS: Shallow stitches placed close to the rim of the perimembranus ventricular septal defect eliminate injury to the right bundle branch.     

New technique for enlargement of the pulmonary outflow tract in corrected transposition of the great arteries [SLL]--a report of 2 cases

New technique for enlargement of the pulmonary outflow tract was performed in two patients with corrected transposition of the great arteries [SLL] associated with atrial septal defect, ventricular septal defect, pulmonary stenosis and mitral regurgitation. The middle of the anterior leaflet of the mitral valve was incised to the valve annulus towards the mid-point of the mitral-pulmonary fibrous continuity. In this approach, anterior node and anterior atrioventricular conduction bundle were securely protected from the surgical incision. The pulmonary annulus was divided posterolaterally and the incision was further extended into the pulmonary trunk to the bifurcation. The pulmonary trunk was enlarged with a fusiform patch of the xenogenous pericardium bearing monocusp. In case 1, St. Jude Medical valve #31 was implanted in the mitral position. In case 2, mitral valvular annuloplasty with Carpentier ring #36 which was deformed to admit enlarged portion of the pulmonary trunk. The VSD was closed through the right atrium, placing the suture on the left side of the septum. However, complete A-V block ensured temporarily due to retraction at the operation in case 1. No conduction disturbance ensured in case 2. This technique can provide some advantage in avoidance of injuries to the anterior node and the anterior atrioventricular conduction bundle. Application of this technique to the corrected transposition of the great arteries without mitral regurgitation is to be further evaluated.     

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.     

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.     

Accessory atrioventricular node and bundle: a cause of antidromic reentry tachycardia.

Two patients are described with antidromic reentry tachycardia successfully treated by interruption of an anterior septal accessory atrioventricular node and bundle. This anomalous connection resembles an atrioventricular conduction sling seen in complex congenital heart malformations. It has atrioventricular node-like properties, is located in the anterior septal area, will only conduct antegrade, and has an insulated connection to the right bundle branch. Rather than nodoventricular, nodofascicular, atriofascicular, or Mahaim, a more appropriate label for the connection is accessory atrioventricular node and bundle.     

Surgical Significance of Morphological Variations in the Atrial Septum in Atrioventricular Septal Defect for Determination of the Site of Penetration of the Atrioventricular Conduction Axis

The morphological variation in the recognized landmarks for the atrioventricular conduction system was studied grossly in 94 hearts with atrioventricular septal defect, assessing 20 hearts with normal atrioventricular septation as a control. In all the hearts with intact atrioventricular septal structures, the tendon of Todaro demarcated the superior boundary of the triangle of Koch. In hearts with atrioventricular septal defect, however, the landmarks for the conduction axis made up a separate nodal triangle. The tendon of Todaro, along with a bridging tendon not found in the normal heart, were variably developed in hearts with atrioventricular septal defect and formed a further triangle unrelated to the axis for atrioventricular conduction. The opening of the coronary sinus was also variable in its location and size. It was the location of the inferior bridging leaflet as it crossed the ventricular septum that was the best surgical landmark to the site of penetration of the atrioventricular conduction axis.     

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.     

Surgical substrates of postoperative junctional ectopic tachycardia in congenital heart defects

BACKGROUND: Junctional ectopic tachycardia is a major cause of postoperative morbidity after surgery for congenital cardiac disease. To elucidate the mechanism of junctional ectopic tachycardia, surgical correlations were studied in four types of congenital heart defects involving closure of a ventricular septal defect, relief of right ventricular outflow tract obstruction, or both. METHODS: Between 1997 and 1999, a total of 343 consecutive patients underwent repair of tetralogy of Fallot (n = 114), common truncus arteriosus (n = 10), ventricular septal defect (n = 161), and atrioventricular septal defect (n = 58). Variables studied included demographic and bypass data, surgical approaches toward ventricular septal defect closure and relief of right ventricular outflow tract obstruction, and resection as opposed to division of muscle bundles. RESULTS: Junctional ectopic tachycardia occurred most frequently after repair of tetralogy of Fallot (n = 25; 21.9%), with no cases occurring after repair of common trunk, 6 occurring after repair of ventricular septal defect (3.7%), and 6 occurring after repair of atrioventricular septal defect (10.3%). Stepwise logistic regression revealed that resection of muscle bundles (P <.0001), higher bypass temperatures (P <.03), and relief of right ventricular outflow tract obstruction through the right atrium (P <.05) significantly and independently predicted postoperative junctional ectopic tachycardia. CONCLUSIONS: Relief of right ventricular outflow tract obstruction appears to be more important in the causation of junctional ectopic tachycardia than does ventricular septal defect closure, which may explain the higher incidence of this complication after tetralogy of Fallot repair. Muscular resection seems to be more arrhythmogenic than is simple division. Increased traction through the right atrium for relief of right ventricular outflow tract obstruction would fit the hypothesis that enhanced automaticity of the His bundle, the morphologic substrate for junctional ectopic tachycardia, may result from direct trauma or infiltrative hemorrhage of the conduction system. When feasible, techniques avoiding both extensive muscle resection and excessive traction should be applied during resection of right ventricular outflow tract obstruction.     

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.     

A histological study of surgical landmarks for the specialized atrioventricular conduction system, with particular reference to the papillary muscle

Surgical landmarks of the conduction system were histologically evaluated in 29 cardiac specimens. The distribution of the system was grossly inherent to the type of ventricular septal defect as classified by Soto and coworkers, although it varied individually. The relationship of the right bundle branch (RBB) to the papillary muscles was of surgical interest. In defects unrelated to maldevelopment of the septum of the conus, the RBB passed beneath or slightly anterior to upper accessory papillary muscles (AcPMs) and posterior to the medial papillary muscle (MPM), regardless of the subtype of defect. In defects caused by maldevelopment, such as tetralogy of Fallot, it passed anterior to the MPM. Such data support the hypothesis that the RBB descends beneath or anterior to embryological upper AcPMs, whatever the morphological role may be, because of the supposedly independent developmental origin of the MPM and AcPMs. The relationship between the RBB and upper AcPMs appeared further modified by the attitude of the trabecula septomarginalis. Our improved clinical results have demonstrated that such information offers a gross but practical guide for prevention of conduction disturbances.     

Morphology of ventricular septal defects in complete transposition. Surgical implications.

Postmortem examination of 62 hearts with complete transposition (concordant atrioventricular and discordant ventriculoarterial connections) and an accompanying ventricular septal defect was performed to determine the morphologic variability of ventricular septal defects and to explore the surgical implications of these defects. Particular attention was directed toward assessing alignment of the outlet septum relative to the muscular septum. Coronary arterial distributions were also evaluated, but specific patterns of distribution did not correlate with morphology of the defect. Of 49 hearts with a normally aligned outlet septum, there were 24 perimembranous, 21 muscular, and 2 doubly committed and juxtaarterial defects. Two hearts had both perimembranous and muscular defects. Twelve of the 21 muscular defects were "central," being surrounded entirely by muscle and located just below the leaflets of the pulmonary valve, and 9 were located in the inlet or apical trabecular septum. There were 13 hearts with malalignment of the outlet septum, anteriorly in 11 and posteriorly in 2. All with anterior malalignment had a subpulmonary defect that was perimembranous in 7 and muscular in 4. Both defects with posterior malalignment had a subaortic perimembranous defect. Because variations in morphology of a ventricular septal defect have a direct impact on selection of the most suitable surgical repair, specific operative approaches are discussed.     

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.     

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.     

Septum primum defect repair.

Two technical maneuvers in septum primum defect repair have resulted in improved mitral valve function and security against heart block. One maneuver, critical to restoring mitral competence, is accurate reconstruction of the leading edge of the mitral valve. A second maneuver, suturing the septal defect patch at its inferior aspect to the mitral valve near the annulus instead of to the inferior septal defect margin or to the tricuspid annulus, eliminates the hazard of atrioventricular node or bundle injury.     

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.     

Simplified single patch technique for the repair of atrioventricular septal defect.

OBJECTIVE: Because of the complexity of traditional 1- and 2-patch techniques for the repair of complete atrioventricular septal defect, we modified our repair technique to avoid the use of any ventricular septal patch material. We report our prospective experience with this simplified 1-patch technique. METHOD: Forty-seven consecutive patients between May 1995 and August 1998 underwent repair with the use of this technique without modification. Repair was done in all patients by direct suturing of the common atrioventricular valve leaflets to the crest of the ventricular septum. No division of valve leaflets was necessary. A single pericardial patch was used to close the defect in the atrial septal component. Follow-up included electrocardiography and echocardiographic assessment of ventricular function, atrioventricular valve function, and adequacy of the left ventricular outflow tract. RESULTS: There were 2 deaths (4%), only 1 cardiac related, in the series. There were 17 male patients and 30 female patients. Mean age at repair was 5.6 months (median, 3.4 months). Associated lesions were repaired in 19 patients (40%). Mean follow-up was 1.85 years (median, 1.9 years). There was no heart block. There were no significant residual ventricular septal defects detected and no left ventricular outflow tract obstruction seen on echocardiography in any patient to date. Mitral valve status after operation was assessed as no incompetence in 13 patients (28%), minimal in 19 patients (40%), mild in 12 patients (26%), and moderate in 3 patients (6%). CONCLUSION: The repair of complete atrioventricular septal defect by direct suturing of the atrioventricular valve leaflets to the crest of the ventricular septum with a single-patch technique greatly simplifies the repair and does not lead to left ventricular outflow tract obstruction nor interfere with valve function.     

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.     

Repair of Ventricular Septal Rupture Through the Right Atrium

A bstract The right atrial approach for repair of ventricular septal rupture associated with myocardial infarction is an alternative technique to the conventional approach of exposing the septum through the left ventricle. This technique may be combined with mitral valve replacement, infarct excision, or aneurysm resection, by avoiding a direct incision in the ventricle reduce postrepair bleeding and impairment of ventricular contractile function. We present a case of ventricular septal rupture repaired through the right atrium and review our surgical technique. This technique may be applied to most cases of ventricular septal rupture, and is particularly useful when the ventricular wall is not infarcted or aneurysmal, and the defect involves the central portion of the muscular septum, the inlet septum, and the subaortic and membranous area.     

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.