Surgical management of straddling atrioventricular valve

Conversion of prior univentricular repairs to septated circulation: Case selection, challenges, and outcomes

Objectives

Complex congenital heart defects that present earlier in life are sometimes channelled in the single ventricle pathway, because of anatomical or logistic challenges involved in biventricular correction. Given the long-term functional and survival advantage, and with the surgeons' improved understanding of the cardiac anatomy, we have consciously explored the feasibility of a biventricular repair in these patients when they presented later for Fontan completion. We present a single institution's 10-year experience in achieving biventricular septation of prior univentricular repairs, the technical and physiological challenges and the surgical outcomes.

Methods

Between June 2010 and December 2019, 246 patients were channelized in the single ventricle pathway, of which 32 patients were identified as potential biventricular candidates at the time of evaluation for Fontan palliation, considering their anatomic feasibility. The surgical technique involves routing of the left ventricle to the aorta across the ventricular septal defect, ensuring an adequate sized right ventricular cavity, establishing right ventricle-pulmonary artery continuity and taking down the Glenn shunt with rerouting of the superior vena cava to the right atrium. This is a retrospective study where we reviewed the unique physiological and surgical characteristics of this subset of patients and analysed their surgical outcomes and complications.

Results

Biventricular conversion was achieved in all cases except in 3 patients, who had the Glenn shunt retained leading to a one and a half ventricle repair. The average age of the patients was 4.9 years of whom 18 were male. The average cardiopulmonary bypass time was 371 min with an average cross clamp time of 162 min. There was one mortality in a patient with corrected transposition of great arteries (c-TGA) with extensive arterio-venous malformations (AVMs). At a median follow-up of 60 months, all patients remained symptom free except two with NYHA II symptoms, one being treated for branch pulmonary artery stenosis with balloon dilatation and the other with multiple AVMs who needed coil closure. One patient with branch pulmonary artery (PA) stenosis required balloon dilatation and stent placement.

Conclusion

The possibility of achieving the surgical goal in this unique subset of patients evolves with the progressive experience of the congenital heart surgeon. Case selection is a crucial aspect in achieving the desired outcome, and this 'borderline' substrate is often recognized at the time of evaluation for the Fontan completion. A comprehensive preoperative imaging and planning helps in achieving the surgical septation and reconnection to achieve the desired physiological circulation. Though technically challenging, the surgery has excellent short- and mid-term outcomes as evidenced by our 10-year experience.

Staged Biventricular Repair-Oriented Strategy in Borderline Biventricular Repair Candidates with Ventricular Septal Defect

Although borderline biventricular repair (BVR) candidates unsuitable for primary BVR are often subjected to single-ventricle repair (SVR), some of them reach BVR by staged strategy. We evaluated our staged BVR-oriented strategy in borderline BVR candidates with ventricular septal defect (VSD) in whom a BVR/SVR decision was deferred beyond the neonatal period. Forty-two patients were treated with the approach between 1991 and 2012. They had been followed toward BVR until it was judged impossible. Outcomes, time course toward definitive repair (DR: BVR, SVR, or 1 + 1/2 ventricle repair), and hemodynamics were reviewed. A total of 57 palliative surgeries were performed before BVR or bidirectional Glenn (BDG), namely procedures to control pulmonary blood flow in 40, to improve mixing in 5, and to promote left ventricle (LV) growth in 5. LV growth was achieved in four patients. There were three cardiac deaths. Except for four awaiting patients, 19 reached BVR (50 %), 11 patients were converted to other than BVR, and 28 patients achieved DR (74 %) at the median age of 30.9 months. Cardiac cath before BVR or BDG performed at the median age of 22.5 months revealed well-preserved pulmonary vasculature with the median pulmonary artery pressure of 14 mmHg, except three patients unsuitable for SVR. In conclusion, our staged BVR-oriented strategy required longer time course and more complex palliative surgeries compared with a simple SVR strategy. Leaving open the possibility of a late crossover to an SVR pathway is mandatory when adopting staged BVR-oriented strategy in these complex patients.

[Criss-cross heart with atrioventricular discordance, straddling A-V valve, double outlet right ventricle and preexcitation]

We report the case of a newborn with cyanosis, dyspnea, and supraventricular tachycardia due to reentry with good response to medical therapy. The diagnosis was made by echocardiography. The patient died suddenly at 6 days of follow-up. Necropsy confirmed the following anomaly: criss-cross heart with straddling right atrioventricular valve, and left atrioventricular valve stenosis connected to the anterior trabeculated ventricle giving rise to the pulmonary artery and aorta.Precocious rotation when septal closure is not concluded favors atrioventricular valve anomalies and rhythm disorders.

Biventricular repair for double-outlet right ventricle

Double-outlet right ventricle (DORV) is a heart malformation that describes an anomalous ventriculoarterial connection which can be associated with considerable variant of associated lesions. When this malformation is present with two ventricles, biventricular repair is feasible in the vast majority of cases. This report describes the surgical techniques for biventricular repair in all forms of encountered DORV, as well as the surgical strategy employed at our institution. Copyright 2000 by W.B. Saunders Company

Transthoracic three-dimensional echocardiography for the assessment of straddling tricuspid or mitral valves

BACKGROUND

The advent of 3D echocardiography has provided a technique which, potentially, could afford significant additional information over conventional cross-sectional echocardiography in the assessment of patients with straddling atrioventricular valves prior to surgical correction.

METHODS

Eight patients, aged from 1 month to 9.2 years, were examined with 3D echocardiography. All but three had discordant ventriculoarterial connections or double outlet right ventricle. Data suitable for reconstruction was acquired with transthoracic scanning. Right and left ventricular volumes were calculated in the 3D dataset.

RESULTS

3D echocardiography proved capable of defining the exact degree of straddling by imaging the proportion of tension apparatus attached to either side of the ventricular septum. It was able also to display the atrioventricular junction "en face", thus permitting identification of the precise site of insertion of the muscular ventricular septum relative to the atrioventricular junction. This made it possible first, to calculate the degree of valvar override, and second, to predict the location of the penetrating atrioventricular bundle. End-diastolic volume of the right ventricle in those with straddling tricuspid valves was 73 (61-83)% of normal, and, of the left ventricle in those with mitral valvar straddling 71 (40-97)% of normal.

CONCLUSIONS

3D echocardiography can aid in planning the optimal surgical procedure in patients with straddling or overrriding atrioventricular valves, as it provides diagnostic information superior to standard cross-sectional techniques. It also allows for exact measurement of the volumes of the respective ventricles.

Surgical management of the straddling mitral valve in the biventricular heart

BACKGROUND

The straddling mitral valve in the biventricular heart is a rare condition that may complicate biventricular repair.

METHODS

Treatment and outcomes in 5 consecutive patients who underwent primary repair between 1992 and 1997 were reviewed. Their ages at repair ranged from 2 months to 8 years. Three patients had a double-outlet right ventricle with a subaortic (n = 2) or subpulmonary (n = 1) ventricular septal defect. Two patients had transposition of the great arteries (S,D,D), a ventricular septal defect, and left ventricular outflow tract obstruction. The attachments of the papillary muscles of the straddling mitral valves were located on the right ventricular aspect of the ventricular septum. Four patients underwent baffle partitioning of the ventricular cavity. The baffle suture line was used to secure the chordae tendineae crossing the ventricular septal defect, or was intentionally omitted at the papillary muscle. The right ventricular outflow tract was reconstructed with patch augmentation, an extracardiac conduit, or an arterial switch operation. One patient with transposition who had a giant papillary muscle to the straddling mitral valve associated with abnormal insertion of the tricuspid valve on the conal septum underwent univentricular repair.

RESULTS

There were no early or late postoperative deaths. There was no mitral valve dysfunction, left ventricular outflow tract obstruction, or heart block in the 4 patients who underwent biventricular repair.

CONCLUSIONS

Although there are several exceptional situations in which ventricular partitioning may result in early and late complications, a straddling mitral valve does not preclude biventricular repair.

Straddling tricuspid valve as a sign of ventriculoatrial malalignment: A morphometric study of 19 postmortem cases

BACKGROUND

Straddling tricuspid valve, despite extensive investigation, remains an incompletely understood form of complex congenital heart disease.

METHODS

A morphometric study of 19 postmortem cases of straddling tricuspid valve was performed, and the results were compared with 32 normal control heart specimens.

RESULTS

In straddling tricuspid valve, marked malalignment of the ventricles was always found relative to the atria. The angle between the ventricular septum and the atrial septum in the short-axis projection averaged 61 degrees +/- 24 degrees, the normal ventriculoatrial septal angle averaging 5 degrees +/- 2 degrees (P <. 001). The right ventricular sinus (inflow tract) was significantly smaller than the left (P <.01). A ventricular septal defect was present in 79%: atrioventricular canal type in 42%, atrioventricular canal type confluent with a conoventricular defect in 26%, and a conoventricular defect in 11%. When the straddling tricuspid valve adhered to the crest of the muscular ventricular septum (n = 4 cases, 21%), the 2 salient findings were (1) an intact ventricular septum and (2) double-outlet right atrium. The nonstraddling part of the tricuspid valve opened into the small right ventricle. The straddling part of the tricuspid valve opened into the larger left ventricle. The mitral valve also opened into the left ventricle. Hence hearts with double-outlet right atrium had 3 atrioventricular valves. Congenital mitral stenosis was present in 26% of this series.

CONCLUSION

Straddling tricuspid valve was always characterized by marked ventriculoatrial malalignment, indicated by an abnormally large ventriculoatrial septal angle, best seen in the short-axis projection.

Suspension of straddling tricuspid valve chordae into the appropriate ventricle

In 2 children with an inlet ventricular septal defect and straddling chordae tendineae of the septal leaflet of the tricuspid valve to the posteromedial papillary muscle of the mitral valve and to an accessory papillary muscle in the left ventricle, the straddling chordae were excised with a wedge of posteromedial papillary muscle and with the top segment of the accessory papillary muscle, respectively. After patch closure of the ventricular septal defect, the papillary muscle segment with its group of chordae was anchored to the right ventricular septum with resulting competence of the tricuspid valve. In contrast to the traditional repair technique, the reported modification is applicable when the straddling chordae insert into a papillary muscle of the mitral valve. In addition, various disadvantages related to the construction of a complex baffle in the inappropriate ventricle are avoided.

Surgical approaches for double-outlet right ventricle or transposition of the great arteries associated with straddling atrioventricular valves

The surgical management of patients with double-outlet right ventricle or transposition of the great arteries and straddling atrioventricular valves remains a subject of controversy. Biventricular repair has theoretic advantages because it establishes normal anatomy and physiology. In some instances, however, it seems to carry too high operative risk, and a univentricular heart repair is preferred. Since 1984, we have operated on 34 patients with double-outlet right ventricle (n = 15) or transposition of the great arteries (n = 19) with isolated straddling tricuspid valve (n = 17), isolated straddling mitral valve (n = 9), both mitral and tricuspid straddling (n = 2), or abnormal insertion of tricuspid (n = 7) or mitral (n = 2) chordae in the left ventricular outlet, precluding an adequate tunnel construction. Straddling was categorized according to the location of the papillary muscle insertion in the opposite ventricular chamber: type A, on the edge of the ventricular septal defect (n = 14); type B, on the opposite side of the ventricular septum away from the edge of the defect (n = 8); type C, on the free wall of the opposite ventricular chamber (n = 8). Abnormal chordal insertions were classified according to the location of their attachments around the edges of the defect. Three types of chordal distribution were identified: on the aortic conus, on the pulmonary conus crossing the ventricular septal defect, or around the defect closing it like a curtain. All but three patients had two ventricles of adequate size. Sixteen patients underwent palliation. Median age at the definitive operation was 6.5 months (range 1 to 130 months). Thirty patients underwent a biventricular repair and four had a univentricular repair. Biventricular repair was achieved by an arterial switch operation in 18 patients and by tunnel construction from the left ventricle to the aorta in 12. In isolated straddling of types A and B, the ventricular septal defect was closed by adjusting the septal patch on the ventricular side above the straddled papillary muscle. In type C, the patch was sewn over the papillary muscle by applying it on the septum. In double straddling, the ventricular septum was incised between the two papillary muscles, and an ellipsoid patch was used to reconstruct the septal defect, directing each subvalvular apparatus into its own ventricular chamber. When the abnormal chordae in the left outflow tract inserted on the aortic or pulmonary conus, the conus was incised and tailored to make a flap, leaving an unobstructed left ventricular outflow tract. In two patients the subvalvular apparatus was resected and reattached to the patch. Curtainlike chordae were a contraindication to biventricular repair in double-outlet right ventricle but not in transposition. There were four early deaths and one late death, all occurring in the group having biventricular repair. Death was due to myocardial ischemia (n = 1), right ventricular hypoplasia (n = 1), pulmonary hypertension (n = 1), and residual subaortic stenosis (n = 1). Two patients had moderate to severe postoperative atrioventricular valve incompetence, caused by a cleft in the mitral valve in one patient. Three patients were reoperated on for subaortic stenosis (n = 1), pulmonary stenosis (n = 1), and mitral regurgitation (n = 1). Mean follow-up of 30.7 +/- 19.4 months was achieved in the survivors. All but one patient (univentricular repair) were in New York Heart Association class I, without atrioventricular valve incompetence. Actuarial survival at 4 years was 85.3% +/- 3%. We conclude that straddling or abnormal distribution of chordae tendineae of the atrioventricular valves does not preclude biventricular repair in double-outlet right ventricle or transposition of the great arteries provided that the ventricles are of adequate size. Curtainlike abnormal tricuspid chordae remain a contraindication to biventricular repair in double-outlet right ventricle.

Mitral atresia with a large left ventricle and an underdeveloped or absent right ventricular sinus: clinical profile, anatomic data and surgical considerations

In mitral atresia with a large left ventricle, the tricuspid valve is either straddling and biventricular or entirely left ventricular. To learn how to assess the identity of the tricuspid valve in such cases 15 heart specimens were examined as well as the echocardiograms of 10 living patients. When the right ventricular sinus was underdeveloped (11 cases), a straddling tricuspid valve was present; when it was absent (14 cases), the tricuspid valve was entirely left ventricular. Regardless of biventricular or exclusively left ventricular attachments, the tricuspid valve was tricommissural (at postmortem examination or on echocardiography) in 22 cases (88%). Its chordal attachments showed considerable variations but were usually paraseptal or on the ventricular septal crest or conal septum. When biventricular, the tricuspid valve straddled through an inlet ventricular septal defect. Clinical or anatomic evidence, or both, of tricuspid regurgitation was present in 14 cases (56%). It is concluded that 1) the identity of the atrioventricular valves is reflected in their chordal attachments more accurately than in their leaflet morphology and depends primarily on the type of ventricular loop present; 2) as a rule, the tricuspid valve is right-sided in D-looped and left-sided in L-looped ventricles; 3) valve identity expressed as the number and position of the papillary muscle attachments is generally recognizable echocardiographically and can be used to diagnose the type of ventricular loop that is present; and 4) the presence and degree of tricuspid regurgitation deserve attention when choosing optimal palliative surgery.

Straddling mitral valve with hypoplastic right ventricle, crisscross atrioventricular relations, double outlet right ventricle and dextrocardia: morphologic, diagnostic and surgical considerations

The clinical, surgical and morphologic findings in five cases of a rare form of straddling mitral valve are presented. Three patients were diagnosed by two-dimensional echocardiography, cardiac catheterization and angiocardiography and two had diagnostic confirmation at autopsy. All five cases shared a distinctive and consistent combination of anomalies: 1) dextrocardia; 2) visceroatrial situs solitus, concordant ventricular D-loop and double outlet right ventricle with the aorta positioned to the left of and anterior to the pulmonary artery; 3) hypoplasia of right ventricular inflow (sinus) with tricuspid valve stenosis or hypoplasia; 4) large right ventricular infundibulum (outflow); 5) malalignment conoventricular septal defect; 6) straddling mitral valve with chordal attachments to the left ventricle and right ventricular infundibulum; 7) severe subpulmonary stenosis with well developed pulmonary arteries; and 8) superoinferior ventricles with crisscross atrioventricular (AV) relations. The degree of malalignment between the atrial and ventricular septa was studied quantitatively by measuring the AV septal angle projected on the frontal plane. The AV septal angle in the two postmortem cases was 150 degrees, reflecting marked malalignment of the ventricles relative to the atria. This AV malalignment appears to play an important role in the morphogenesis of straddling mitral valve. As judged by a companion study of seven postmortem cases, the more common form of straddling mitral valve with a hypertrophied and enlarged right ventricular sinus had less severe ventricular malposition than did the five rare study cases with hypoplastic right ventricular sinus. A competent mitral valve, low pulmonary vascular resistance and low left ventricular end-diastolic pressure were found at cardiac catheterization in the three living patients who underwent a modified Fontan procedure and are doing well 2.2 to 5.8 years postoperatively.

Exercise responses in patients with congenital heart disease after Fontan repair: patterns and determinants of performance

After a Fontan repair for congenital heart disease, 42 patients underwent graded supine bicycle exercise tests at levels relevant to normal daily activities. Results were compared with those of 28 age-matched normal control subjects. At rest, the cardiac index, stroke index and systolic blood pressure were comparable in both groups, but increases with exercise were smaller in the patients with a Fontan circulation. The heart rate at rest was higher in the Fontan group, but this difference disappeared as soon as exercise started. To determine whether there are limitations intrinsic to the Fontan circulation at these levels of exercise, the 10 best performers were compared with 10 age-matched control subjects; no differences were found in cardiac index, stroke index, heart rate or blood pressure at any exercise level. Analysis of the determinants of cardiac output showed that at the other end of the spectrum poor performance after a Fontan operation did not result from inadequate levels of heart rate, but from an inability to increase or maintain stroke volume. Multivariate analysis demonstrated that impairment of ventricular contractility, only when severe, predicted limited performance. There was no evidence of increased afterload, particularly in the poor performers. Therefore, ventricular filling, which is determined primarily by the pulmonary vascular bed, appears to be a major determinant of functional result after a Fontan repair.

Straddling tricuspid valve without a ventricular septal defect

A four year old girl with pulmonary atresia had a straddling tricuspid valve without an interventricular communication. The overriding tricuspid valve had two orifices, which connected with the right and the left ventricles. Valve tissue separated both orifices and was firmly connected to the crest of the ventricular septum, thus sealing off the expected interventricular communication. Surgical correction was performed and the outcome was satisfactory.

Surgical repair of superoinferior ventricles: experience with 3 patients

Superoinferior ventricles are a rare anomaly characterized by a horizontal ventricular septum and a hypoplastic right ventricular sinus localized anterosuperiorly to the left ventricle. This anomaly frequently is accompanied by malformation of the atrioventricular valves. A large ventricular septal defect is always present, and anomalies of the ventriculoarterial relations are common. The results of surgical repair of this complex lesion have been poor. Our recent surgical experience with 3 patients, 2 of whom are well 36 and 38 months postoperatively, suggests a hopeful outcome for the repair of this complex anomaly. The surgical approach was different in each of the 3 patients, demonstrating the need for a precise echocardiographic and angiocardiographic preoperative description of the cardiac anatomy to appropriately repair the multiple variants of this complex anomaly.

Straddling atrioventricular valve: two-dimensional echocardiographic diagnosis, classification and surgical implications

The usefulness of subclassifying the anatomic variations of straddling and overriding atrioventricular (AV) valve by 2-dimensional echocardiographic observation were evaluated. Chordae straddling into a contralateral ventricle were subdivided into type A (chordae inserting into the contralateral ventricle near the crest of the ventricular septum), type B (chordae inserting along the contralateral ventricular septum) and type C (chordae inserting into the free wall or papillary muscles of the contralateral ventricle). Overriding AV valve anulus was described as minor (less than 50% of the anulus committed to the contralateral ventricle), major (about 50% of the anulus committed to each ventricle), and double-inlet ventricle (greater than 50% of both AV valves committed to a single ventricular chamber). In 52 patients straddling AV valve was diagnosed by echocardiography and confirmed by direct examination at surgery or autopsy. In 60 of 66 straddling AV valves (91%), the diagnosis and the degree of straddling (type A, B or C) were correctly identified by 2-D echocardiography. Major associated cardiac defects included double-outlet right ventricle (31%), complete transposition (23%), corrected transposition (19%), double-inlet ventricle (19%) and other complex defects (8%). Twenty-two patients (42%) had right-sided straddling, 21 (40%) had left-sided straddling and 9 (17%) had straddling of both AV valves. In 41% of the patients, straddling AV valve had a major impact on the type of surgery or the surgical outcome. Of these valves, 52% were type C (severe), 26% type B and 22% type A straddling.(ABSTRACT TRUNCATED AT 250 WORDS)

A new method of closing the ventricular septal defect in corrected transposition of the great arteries

A new method of closing a perimembranous malalignment ventricular septal defect (VSD) in corrected transposition of the great arteries (TGA) of the [S,L,L] type is presented. The method consists of combined approaches to the VSD through both a right atriotomy and an aortotomy without a ventriculotomy. The VSD is patched obliquely from the morphological right ventricular side of the septum, cranially through the aortic valve to the left ventricular side of the septum, caudally through the mitral valve. Although this method has been successfully applied in only one adult patient, some advantages may be expected: (1) prevention of trauma to the His bundle, which runs along the anterosuperior rim of the VSD on the left ventricular side; and (2) prevention of trauma to the tricuspid, mitral, and aortic valves without having to open the ventricles. We believe that this new method warrants a further trial as possibly better for closure of the VSD in corrected TGA of the [S,L,L] type.

Criss-cross heart with straddling right atrioventricular valve

Angiocardiographic appearance of a criss-cross heart with straddling tricuspid valve has been presented. Atrial situs was normal and the right atrium was connected to the morphological right ventricle situated superiorly and to the left of the left ventricle. The left atrium was connected to the morphological left ventricle situated inferiorly and to the right of the right ventricle. The interventricular septum was horizontal in position. Both great arteries arose from the right ventricle with the anterior aorta. The case was concluded as a criss-cross heart with concordant atrioventricular (A-V) connection and double outlet right ventricle (DORV). Straddling of the right A-V valve was recognized in another institution by two-dimensional (2-D) echocardiography and confirmed by right atrial angiography in our institution. The value of combined investigation with selective four-chamber angiography, especially including right atrial angiography and 2-D echocardiography in the diagnosis of such complex cardiac anomalies has been stressed.

Successful repair of criss-cross heart using modified Fontan operation

A five-year-old girl with concordant crossing of atrioventricular connection, hypoplastic tricuspid valve, straddling mitral valve, 1-transposition of the great arteries, and other anomalies was operated upon. Modified Fontan operation was beneficial for such a complex cardiac anomaly.

Univentricular heart: can we alter the natural history?

Surgical treatment must be considered for patients with univentricular heart in view of their poor natural history. Since one of the major factors influencing the natural history of this malformation is the amount of pulmonary blood flow, we discuss the potential surgical options by separately considering the two main pathophysiological situations: univentricular heart with restricted pulmonary blood flow, and univentricular heart with unrestricted pulmonary blood flow. We have reviewed the early and late results of surgical treatment based on our experience with 19 patients and the data from the literature. Temporary relief of symptoms can be provided by palliative operations (systemic-pulmonary shunt, atrioseptectomy, enlargement of the outlet foramen, pulmonary artery banding, or palliative Mustard or Senning procedure). "Corrective" surgery, by means of either a modified Fontan operation or ventricular septation, carries a high early mortality (about 30%) and a high early and late morbidity, with only 50% of survivors enjoying an asymptomatic life. Studies of the long-term efficacy of palliative operations as well as our experience and that of others with "corrective" operations, which have a relatively short follow-up, do not yet indicate whether presently available surgical procedures can alter the natural history of patients with univentricular heart.

Rest and exercise hemodynamics after the Fontan procedure

Sixteen consecutive patients (12 with tricuspid atresia) underwent a Fontan procedure, with no operative deaths. There were three late deaths. Eleven of the survivors were electively catheterized 4-25 months postoperatively. Rest and exercise hemodynamics were measured in five patients, and resting hemodynamics alone were measured in three. All exercised patients were New York Heart Association class I Cardiac index was low at rest (2.3 +/- 0.61/min/m2) and during exercise (4.9 +/- 1.11/min/m2) due to a low stroke index both at rest (28 ml) and exercise (35 ml). Accordingly, mixed venous oxygen saturations were decreased (66% at rest and 31% during exercise). These values are significantly lower than those at rest and during exercise from 23 control patients of similar age and size. Heart rates, pulmonary vascular resistances, and left ventricular filling pressures appeared normal both at rest and during exercise. High right atrial pressure at rest (15 mm Hg) was associated with minimal conduit gradient (2 mm Hg). However, exercise increased the mean conduit gradient to 8 mm Hg, demonstrating significant functional conduit obstruction. As expected, the cardiovascular response to exercise is abnormal after the Fontan procedure, even in asymptomatic patients. This abnormal response may be exacerbated by conduit obstruction, and conduit obstruction may not be apparent during resting studies.

Straddling mitral and tricuspid valves: morphologic differences and developmental backgrounds

The anatomy of 25 hearts with a straddling mitral or tricuspid valve, or both, is described. Malalignment of atrial and ventricular septa is an essential feature of a straddling tricuspid valve, creating an inlet septal defect. Across this defect, the tricuspid valve straddles into the opposite (left ventricular) chamber, where it is separated from the mitral valve by a posterior muscular ridge, the posteromedial muscle. A straddling mitral valve requires an infundibular septal defect, predominantly of the malalignment type, in which the anterior part of the ventricular septum deviates to the left of the infundibular septum. The mitral valve straddles into the opposite (right ventricular) chamber, anterior to the trabecula septomarginalis. From normal developmental stages, it is concluded that valve formation takes place only after completion of ventricular septation. Any malformation of the valves is therefore considered to be superimposed on a primary malformation of the septum. The ventricular septum itself develops from three different components. Malseptation in the inlet portion of the embryonic heart lead to the characteristic septal malformation seen in straddling tricuspid valve. Malseptation in the outlet portion may lead to the septal malformation that characterizes straddling mitral valve.

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

Images

The atrioventricular junction in the univentricular heart: a two-dimensional echocardiographic analysis

The atrioventricular junction of 40 patients with univentricular heart was evaluated by two-dimensional echocardiography. The apical 4 chamber view optimally imaged the atrioventricular junction, and allowed determination of the type of atrioventricular connection: double inlet, common atrioventricular orifice, and absent right or left atrioventricular connection. When double inlet to 1 ventricle was demonstrated, the 4 chamber view allowed immediate comparison of the form and function of the right and left atrioventricular valves. Because anomalies of the atrioventricular valves frequently complicate the univentricular heart, two-dimensional echocardiographic assessment is a most important adjunct to the preoperative investigation of these patients.

Detection and assessment of straddling and overriding atrioventricular valves by two dimensional echocardiography

Sixteen patients with a straddling tricuspid and two with a straddling mitral valve were identified by two dimensional echocardiography. In all but one the atrioventricular valves appeared at the same level, indicating absence of the ventriculoatrial septum. A straddling valve was diagnosed by identifying subvalvular apparatus from one atrioventricular valve in both chambers, independent of whether they were ventricles or rudimentary chambers. Further confirmation was obtained during real time study where the valve leaflets appeared to fly through the ventricular septal defect. Overriding of the valve annulus was greater than 50% in 12 and less than 50% in five, with one other patient having none detectable. The relation of the central fibrous body to the tip of the interventricular septum was reliable in assessing overriding of greater than 50%, but where it was less than 50% other views were necessary to detect its presence. The diagnosis of straddling with or without overriding of an atrioventricular valve can be reliably made by two dimensional echocardiography, and carries important implications relating to the type of surgical intervention possible, and in those with a straddling tricuspid valve, the position of the atrioventricular node.

Repair of double-outlet right ventricle. Experience of 13 cases

Surgery for double-outlet right ventricle (DORV) was performed in 13 patients between November 1974 and January 1979. Subaortic ventricular septal defect (VSD) was present in 11 patients, complicated forms of DORV in 2 patients and 5 patients had important concomitant cardiac defects. Six infants (mean age 0.6 years) without pulmonary stenosis (PS) required operation because of pulmonary hypertension, whereas the 7 patients with PS underwent surgery at a considerably later stage (mean age 6 years). Interventricular tunnel-repair established continuity between the systemic ventricle and great artery in 12 patients. One case with subpulmonic VSD was managed by transposition of both venous return and arterial outflow, while the use of valved external conduits was generally avoided. Atrial incision was sufficient to permit complete intraventricular repair in 8 patients, including one pulmonary valvulotomy. Important co-existing PS was otherwise treated as in cases of tetralogy of Fallot and required transannular patch grafting in 2 instances. Hospital mortality was 3/13 patients (23%) and mainly confined to serious associated cardiac malformations which were not amenable to correction. All 10 survivors are functionally improved 1.5-5 years after surgery. Clinical and invasive re-evaluation (3 patients) could not identify the development of systemic ventricular outflow tract obstruction. One patient, who underwent enlargement of a restrictive VSD, presented angiographic evidence of a moderate aortic incompetence. No other important complications were associated with the tunnel-repair and none of the 10 survivors had complete heart block.

Straddling right atrioventricular valves in atrioventricular discordance

Four hearts are described in which the right atrioventricular valve, draining a morphologically right atrium, straddled and overrode a septum between a right-sided chamber of left ventricular morphology and a left-sided chamber of right ventricular morphology. The degree of override varied between the straddling valve and was committed by 20-45% to the morphologically right ventricle. The ventriculoarterial connections in the hearts were discordant in one, double outlet from the morphologically right ventricle in two and single outlet via an aorta from the morphologically right ventricle with pulmonary atresia in the other. The straddling valve in one of the cases with double outlet had a dual orifice. Pulmonary stenosis was present in three cases, and pulmonary atresia in the fourth. Study of the conduction system in three of the hearts revealed subtle but important differences from the pattern expected in atrioventricular discordance. Each case had an anterior atrioventricular node and penetrating bundle, but the connection thus formed was more lateral than usual, and in the case with ventriculoarterial discordance, the nonbranching bundle was unrelated to the pulmonary outflow tract. A sling of conduction tissue between the anterior node and the regular node was found in the case with single outlet and pulmonary atresia.

Successful repair of straddling atrioventricular valve by technique used for septation of univentricular heart

Straddling atrioventricular valve (SAVV) is a rare anomaly. Only recently have the premortem diagnostic features been elucidated. Repair of the associated ventricular septal defect poses a considerable technical problem. Corrective operations, infrequently reported, have usually involved replacement of the SAVV. This report describes the successful management of a patient with a straddling left atrioventricular valve in whom the valve was preserved by a technique previously used for septation of the univentricular heart. This technique offers a useful alternative to valve replacement in the management of patients with SAVV.