Surgical Approach to Corrected Transposition of the Great Arteries 

Updated: Jan 06, 2014
Author: Prema Ramaswamy, MD; Chief Editor: Suvro S Sett, MD, FRCSC, FACS 

Overview

Background

Corrected transposition of the great arteries is a rare condition and has been estimated to account for 0.5-1.4% of clinically apparent congenital heart disease cases.[1, 2]  Of this group, probably fewer than 1% of individuals have no associated abnormalities.[3]  In corrected transposition of the great arteries, the left atrium is connected to a right ventricle, from which an aorta arises. Hence, 2 discordant connections occur in sequence.

In 1875, Von Rokitansky first described this condition in 2 cases. In 1919, Weinberger first reported that it is fairly frequently associated with dextrocardia.[4]

Relevant Anatomy

Knowing the position of the atrioventricular (AV) node in this defect is extremely important if injury to it during surgery is to be avoided. Because of the L-looping of the ventricles in this condition, the usual posterior position of the AV node is prevented from reaching the interventricular septum because of the malalignment of the atrial and inlet ventricular septa. An anterior node is present, either alone or in addition to the posterior node, and it is located in the floor of the right atrial wall immediately anterolateral to the interatrial septum. This gives rise to an AV bundle that penetrates the fibrous annulus to make contact with the ventricular myocardium. It then passes anterior to the pulmonic annulus along the morphologic left ventricular side of the septum and subsequently courses anterior and superior to a perimembranous outlet ventricular septal defect (VSD).[5, 6]

This anterior position of the AV node is more commonly reported in situs solitus. In situs inversus, a posteriorly positioned AV node has been described.[7] However, other authors stress that either position of the AV node is possible with any situs.[8]

The coronary arteries arise from the aortic valve sinuses adjacent to each ventricle. The morphologic left coronary artery arises from the right-sided posterior sinus, and the morphologic right coronary artery arises from the left-sided posterior sinus. The most common coronary artery abnormality is a single coronary artery that arises from the right-sided posterior sinus.[9]

Problem

The presence of ventricular inversion (ie, atrioventricular discordance) with ventriculoarterial discordance has been called corrected transposition or physiologically corrected transposition because these 2 anomalies in sequence ensure that blood flow continues in its usual physiologic pathway. However, because this condition is usually associated with other abnormalities, many have commented that it should not be called corrected.[10, 11]

The 4 chambers of the heart have distinct features that identify them regardless of their actual spatial location or connection. Therefore, even if a ventricle is present on the left side, it can be identified as a morphologic right ventricle. The right ventricle is identified by the presence of a muscle tissue that traverses it horizontally near the apex (ie, moderator band) and by the tricuspid valve, which is situated more apically than the mitral valve at its attachment to the crux of the heart. Also, the tricuspid valve has multiple papillary muscle attachments to the septum (unlike the mitral valve, which has none) and is separated from the pulmonary valve by the muscular band of tissue called the crista supraventricularis or conus. The broad triangular shape of the right atrial appendage assists identification of the right atrium because it is different from the narrow, fingerlike left atrial appendage.

In the nomenclature advocated by Van Praagh in 1989, this form of transposition has been designated S,L,L.[12] The S stands for atrial situs solitus, indicating that the morphologic right atrium lies to the right of the morphologic left atrium. The first L is for an L-looped right ventricle or a right ventricle with a left-hand pattern of internal organization. During the process of development in a normal heart, the right ventricle comes to lie on the right side so it undergoes a dextro-loop (ie, d-loop). A d-loop ventricle is one in which the internal pattern of the right ventricle conforms to a right-hand pattern, in which an extended thumb indicates the attachment to the tricuspid valve and in which the fingers indicate the right ventricular outflow tract when the palm is placed on the septal surface. The second L stands for the position of the aortic valve, which is anterior and to the left of the pulmonic valve.

In the normal heart, the aorta is posterior and to the right. In the presence of situs inversus, the nomenclature for corrected transposition is I,D,D. In a detailed study on the pathologic anatomy in 34 specimens with corrected transposition and 2 ventricles, Van Praagh et al found that the segmental classification was S,L,L in 94%, I,D,D in 3%, and S,L,D in 3%.[13]

Pathophysiology

Pathophysiology is determined by the presence and type of associated lesions. When no other defects are present, the path of the blood flow is physiologic; blood from the left atrium enters the right ventricle and is then directed into the aorta, and, on the right side, the deoxygenated blood from the vena cava enters the left ventricle. Because of the ventriculoarterial discordance, the deoxygenated blood is then directed into the pulmonary artery. Thus, the oxygen saturations in the heart chambers and in the great arteries are normal.

The most common anatomic associations include the presence of a ventricular septal defect (VSD), which may be observed in almost 80% of cases and the presence of pulmonary stenosis, which has been reported in approximately 50% of cases.[14, 3] The presence of a VSD causes a systemic-to-pulmonary shunt; however, this is usually balanced because of the protective effect of coexisting pulmonic stenosis.

Tricuspid valve anomalies, including dysplasia, straddling, or Ebsteinlike malformation (with or without regurgitation) are also quite common and are reported in 14-56% of patients.[15, 14] Tricuspid regurgitation in this setting of a systemic ventricle, which is the morphologic right ventricle, is much more ominous than it would be in an otherwise normal heart. Coarctation and interrupted aortic arch have also been frequently reported, but subvalvar and valvar aortic stenosis are quite uncommon.[14, 11] Conduction abnormalities also are common. The reported incidence of complete atrioventricular (AV) block has ranged from 12-33%.[16, 17] Spontaneous progression of AV block has been reported to occur at a rate of 2% per year.[16, 18] Additional rhythm problems include Wolff-Parkinson-White syndrome, supraventricular tachycardia, atrial flutter, and atrial fibrillation.[1, 15, 17]

Etiology

As with almost all forms of congenital heart disease, the causes are thought to be multifactorial. Most of the clinical and surgical retrospective studies have reported a male predominance in corrected transposition.[15, 14]  One study suggested an autosomal recessive mechanism of transmission may be present in some families.[19] Interestingly, they found that transposition of the great arteries was the most common recurrent defect in families with congenitally corrected transposition, suggesting a pathogenetic link between these 2 entities.

Presentation

Patients with isolated corrected transposition of the great arteries may present in adulthood because of abnormal radiography or ECG findings and may have no symptoms, at least for the first 3 or 4 decades of life. See the image below.

A 12-lead ECG demonstrating the characteristic fea A 12-lead ECG demonstrating the characteristic features of corrected transposition Q waves in III, in aVF, and in the right precordial leads.

In a study of 18 patients, Presbitero et al found that rhythm disturbances and tricuspid regurgitation were present more frequently after the third decade of life.[20] They found that this and impaired right ventricular function developed in 66% of patients older than 50 years, causing congestive cardiac failure.

A multi-institutional study confirmed that congestive cardiac failure is common in patients with or without associated cardiac defects.[21] By age 45 years, 67% of patients with associated anomalies and 25% of patients without associated anomalies were in congestive cardiac failure.

Another large study by Rutledge et al confirmed that survival rates are reduced in these patients.[22] They found poor right ventricular function and complete AV canal as risk factors for mortality. Risk factors for progressive right ventricular dysfunction included conventional biventricular repair, complete AV block, and severe tricuspid regurgitation.

Most patients who have associated anomalies present in infancy with a murmur or heart failure. Patients with bradycardia secondary to complete AV block can present at any age. Unless these patients have pulmonary atresia or severe pulmonic stenosis, cyanosis is not present. An important physical finding is the presence of a loud single second heart sound along the upper left sternal border.

Indications

For the rare patients who have corrected transposition and no other associated abnormalities, no treatment may be required because their life expectancy has been reported to be near normal.[23, 24] Presently, the treatment of patients with associated anomalies is predicated on the presence of symptoms (eg, heart failure) caused by a moderate ventricular septal defect (VSD) or on significant objective deterioration, if present, such as progressive right ventricular dilatation, severe tricuspid regurgitation, or complete heart block with a slow escape rate.[25]

The surgical management of even the simple associated defects, such as a VSD or pulmonic stenosis, has been reported to be associated with much higher morbidity and mortality rates in these patients than would occur in a patient with an otherwise normal heart. Furthermore, these procedures may not result in a functional improvement. Also, technically, the approach to address the VSD or the pulmonic stenosis is difficult, and the risk of surgically induced complete heart block is quite high.[25]

Contraindications

Patients with corrected transposition and no other associated abnormalities may not require treatment because their life expectancy has been reported to be near normal.[23, 24] However, no clear consensus has been reached regarding this group of patients at this time. At the other end of the spectrum, a double-switch procedure, as described below, would be contraindicated in patients with severe hypoplasia of either ventricle. These patients should be considered for a Fontan-type repair.

 

Workup

Imaging Studies

Chest radiography

An anteroposterior chest radiograph often reveals the characteristic features, including a straightened upper left heart border caused by the side-by-side great arteries instead of the aorta and the pulmonary arteries twisting around each other, as is observed normally. Cardiomegaly may be observed if associated conditions such as ventricular septal defect (VSD) or tricuspid regurgitation are present. See the image below.

An anteroposterior chest radiograph revealing the An anteroposterior chest radiograph revealing the straightened left heart border formed by the aorta, which is more leftward and anterior than usual.

Echocardiography

Relatively recent advances in the technology of Doppler echocardiography make noninvasively diagnosing this condition possible and allows for great accuracy, not only postnatally but also using fetal echocardiography. Two important, suggested clues have been the presence of a left-sided ventricle with a moderator band and an abnormal parallel orientation of the great arteries.[26]

Because dextrocardia is present in 25% of these patients, the position of the heart within the thorax should be initially determined. All standard views are essential to assess the atrial and ventricular morphology in detail and to look for the commonly associated malformations.

See the images below.

A transthoracic echocardiogram in the apical 4-cha A transthoracic echocardiogram in the apical 4-chamber view illustrating the moderator band in the left-sided ventricle and the apically displaced left atrioventricular valve suggesting that it is the morphologic right ventricle.
A transthoracic echocardiogram in the parasternal A transthoracic echocardiogram in the parasternal short axis view demonstrating the anterior and leftward aorta. The left coronary artery can be observed at the 10-o'clock position.

Other Tests

Electrocardiography (ECG) may provide the most significant clue of this condition. The presence of Q waves over the right precordium (because of reverse septal depolarization) with absent Q waves over the lateral precordium in the absence of other criteria for right ventricular hypertrophy should suggest this defect.

Diagnostic Procedures

Angiocardiography is no longer required for the diagnosis because echocardiographic findings are diagnostic. Real danger of causing complete heart block exists during this procedure because the atrioventricular (AV) bundle is located on the left ventricular side of the septum, and because the left ventricle is connected to the right atrium, it is in the direct path of a catheter in a right heart catheterization.[18]

 

Treatment

Medical Therapy

Treatment of congestive cardiac failure secondary to a ventricular septal defect (VSD) is along the standard lines of management and includes the use of afterload-reducing agents (eg, enalapril), as well as other agents (eg, digoxin, diuretics).

The guidelines from the American College of Cardiology and the American Heart Association state that permanent pacing for complete heart block is indicated for congenital heart block in infants with any type of congenital heart disease and a heart rate of less than 70 beats per minute.[27]

In infants with corrected transposition of the great arteries with associated defects, pacemakers are implanted regardless of the heart rate or symptoms of heart failure. Permanent pacing is also indicated after surgically induced heart block. In other patients with corrected transposition of the great arteries who develop complete heart block spontaneously after infancy, the placement of a pacemaker is usually predicated by the presence of symptoms. Dual-chamber pacing is the preferred modality for almost all of these patients except perhaps in the smallest (< 15 kg), in whom placement of both leads through the superior vena cava may present a risk of thrombosis and obstruction.[28]

Surgical Therapy

Surgical therapy may be palliative, at least initially, which may be a good option in this condition (discussed above), or it may involve complete repair. Palliation includes pulmonary artery banding in infancy for moderate VSDs and modified Blalock Taussig shunts for infants with severe pulmonic stenosis that causes the oxygen saturation level to fall below 75-80%. Pulmonary artery banding has gained added importance because, in addition to palliation, it also serves as a tool by which to train the morphologic left ventricle in preparation for an anatomic repair, as discussed below.

The period of training required for the morphologic left ventricle to assume the position of a systemic ventricle varies with the age of the child, from 2 weeks in an infant to a few months or even longer in an older child.[29] Winlaw et al found that patients older than 16 years were unlikely to achieve an anatomic repair and that the morphologic left ventricular function was a critical determinant of survival.

Complete repair may be either a physiologic or an anatomic repair. In the former, only the associated defects are addressed, but the right ventricle continues to function as the systemic ventricle. An anatomic repair is one in which the morphologic left ventricle is established as the systemic ventricle. This includes alternative surgical approaches, such as double-switch procedures.

A physiologic repair may involve any of the following procedures:

  • VSD closure

  • Relief of pulmonic stenosis

  • Tricuspid valve replacement

An anatomic repair may involve Senning or Mustard (see below) and arterial switch if no pulmonic stenosis is present and Senning or Mustard with Rastelli, which is a right ventricle–to–pulmonary artery (RV-to-PA) conduit, in the presence of pulmonic stenosis

These procedures are theoretically attractive because the morphologic left ventricle then assumes the position of the systemic ventricle and the late failure of the right ventricle, which is a prominent part of the natural history of this condition, may possibly be avoided.

Intraoperative Details

Pulmonary artery banding

If performed as a precursor to an anatomic repair, this procedure has been noted by several groups to be more effective in younger children.[29] Devaney et al stated that they tighten the pulmonary artery band until the interventricular septum moves to the midline and the left ventricular pressure is 80% of systemic.[29]

Ventricular septal defect closure

Most of these defects are perimembranous in nature. The optimal approach to the VSD has been described to be through the right atrium and the morphologic mitral valve.[5] Risk of possible permanent damage to the mitral valve and injury to the AV node is noted. In 1979, de Leval et al described how the VSD could be approached from the right atrium or through a careful low left ventriculotomy to avoid the AV bundle as it courses along the roof of the pulmonary outflow tract.[6] The VSD is then closed, and the stitches are applied to the morphologic right side of the VSD in order to minimize the risk of damaging the conduction tissue. In older patients with larger aortas, the VSD can also be approached through the aorta, and, because this allows exposure of the right ventricular side of the defect, a reduced risk of injury to the AV node is noted.[30]

Relief of pulmonic stenosis

Usually, many causes of pulmonic stenosis are present in this condition. Because the pulmonic valve is wedged between the tricuspid and the mitral valve, its annulus is usually hypoplastic. Also, obstruction may be caused by subpulmonary narrowing secondary to fibromuscular tissue. Because the conduction tissue passes anterior to the pulmonic valve, incisions in this area can cause complete heart block. Thus, for most patients, an extracardiac conduit is required from the left ventricle to the pulmonary artery. Cryopreserved aortic homografts are usually used for this because they are long enough to be able to reach the pulmonary artery. The conduit must also be positioned to the right so that compression from the sternum is not an issue.

Tricuspid valve replacement

Tricuspid regurgitation is common and is associated with a poor long-term prognosis.[11] Exposure for repair is difficult; hence, replacement of the valve is required when tricuspid regurgitation is severe. A mechanical prosthesis is preferred over a bioprosthesis because of its longevity.[5]

Double switch

All of the above procedures leave the right ventricle as the systemic ventricle, the progressive failure of which has been noted in long-term follow-up studies.[23] This was confirmed by a large study that demonstrated that the conventional physiologic biventricular repair is one of the risk factors for progressive right ventricular dysfunction.[22] Hence, an alternative concept of an anatomic repair was first proposed by Ilbawi et al, who performed it in corrected transposition, VSD, and pulmonic stenosis.[31] Since then, several other approaches using 2 surgical techniques have been described.[32]

Senning with arterial switch

The principle of both the Senning and the Mustard operations is that the venous return into the heart is rerouted to the other ventricle.Thus, blood returning in the superior and inferior vena cava is directed via a baffle to the left-sided right ventricle, and the pulmonary venous return is directed to the right-sided ventricle.

An operation such as this in combination with an arterial switch operation essentially ensures that the left ventricle becomes the systemic ventricle and the right one becomes the pulmonary ventricle. However, the left ventricle pressure must be near systemic for an arterial switch to be possible. This may occur if a large VSD is present or if a pulmonary artery band is applied to prepare the left ventricle by causing left ventricular hypertrophy. For the atrial switch, the Senning procedure is preferred because it uses less prosthetic material. With this operation, obstruction to the vena cava or the pulmonary venous return is a potential long-term concern. Also, this combination of surgeries is suitable only in the absence of pulmonic stenosis.

Senning and Rastelli (RV-to-PA conduit with VSD closure)

When pulmonic stenosis is associated, an arterial switch is not suitable because the pulmonic stenosis would then become neoaortic stenosis. Instead, the left ventricle can be routed to the aorta by a baffle, closing the VSD in such a way that blood is directed from the left ventricle to the aorta and the right ventricle is connected to the pulmonary artery with a homograft.

The VSD is optimally closed through a right ventriculotomy, which is required for the conduit placement. This ensures that the sutures for the VSD closure are on the right ventricular side and, hence, reduces risk of injury to the AV node.

One-and-a-half ventricle repair

This operation involves establishing a Glenn shunt for the superior vena cava return, a hemi Senning or Mustard to direct the inferior vena cava blood into the right ventricle, and either an arterial switch or a Rastelli, depending on the presence of pulmonic stenosis. This operation is especially useful in the presence of a small pulmonary ventricle.[33, 34] The following are some of the other advantages of this procedure: (1) no risk of superior vena cava obstruction is noted; (2) the intra-atrial space available for the pulmonary venous return is increased, thus, the risk of obstruction to the pulmonary venous return is reduced; (3) the intra-atrial suture lines are reduced, as is the risk of arrhythmias.

Outcome and Prognosis

The prognosis depends on the associated anatomic malformations and the conduction system abnormalities. Complete heart block is a likely complication during surgery for ventricular septal defect (VSD) closure or relief of the pulmonic stenosis.

Conduction system deterioration

Complete heart block can develop over time at a rate of 2% per year.[16, 18] Surgical intervention also increases the risk of this condition because the conduction tissue is fragile and in an abnormal position.

Right ventricular function

Because the right ventricle is morphologically different from the left ventricle and, in a person with a healthy heart, only sustains pressures that are about one fourth to one fifth that of the systemic circuit, whether this ventricle is able to sustain systemic pressures over a lifetime is an area of concern.

Numerous pathways to ventricular dysfunction are possible for the systemic right ventricle in corrected transposition of the great arteries, such as volume overload from tricuspid regurgitation or a ventricular septal defect (VSD) and conduction and rhythm disturbances.

Studies using equilibrium-gated radionuclide angiocardiography have shown that, although the right ventricular ejection volume increases from rest to peak exercise, it is less than that observed in a normal left ventricle.[35] However, patients with systemic right ventricles who have corrected transposition of the great arteries are able to augment their cardiac output with an increase in both heart rate and stroke volume. This is in contradistinction to patients with D-transposition who have undergone a Senning-type operation and, thus, have a systemic right ventricle and can increase their cardiac output only with an increase in the heart rate.[36]

Right ventricular failure remains a concern; progressive tricuspid regurgitation may be indicative of this failure, and surgical treatment should be considered early when it is noted.[37] Although the timing of tricuspid valve surgery beyond adolescence is still a matter of debate, mortality is low after tricuspid surgery in adult patients with mild-to-moderate right ventricular dysfunction, tricuspid valve function and functional class significantly improve after surgery, and systemic right ventricular function is preserved.[38]

In one retrospective review of 46 patients with congenitally corrected transposition who underwent tricuspid valve replacement for tricuspid regurgitation, the preoperative systemic ventricle ejection fraction (SVEF) was the only independent predictor of the postoperative SVEF after more than a year.[39] The late SVEF was preserved (defined as ≥40%) in 63% of patients who underwent surgery with an SVEF ≥40% compared with 10.5% of patients who underwent surgery with an SVEF < 40%. Hence, the authors of this study suggested considering tricuspid valve replacement earlier while the SVEF is still above 40% and the subpulmonary ventricular pressure below 50 mm Hg.

To mitigate long-term effects with respect to right ventricular failure, some surgeons have advocated the double-switch operation.[32]

Prognosis after surgical correction of associated defects

The operative mortality rate for repair of associated defects is higher than that in patients with normal hearts. In a 1996 publication, Szufladowicz et al reported a 14% hospital mortality rate and a 10-year actuarial survival rate of 70%.[40] Factors contributing to this include the presence of complete heart block and the mirror image coronary artery pattern, which makes placement of the left ventricle to the pulmonary artery conduit technically challenging.[41] Another factor is the development of significant tricuspid regurgitation after surgical repair of the VSD, even when it is mild preoperatively.[42]

Studies comparing outcomes after physiologic and anatomic repairs are limited by their small size. However, the following 2 important studies have addressed this issue:

  • The first is a metaanalysis of 11 studies involving 124 patients.[43] In this study, only the immediate outcome (ie, in-hospital mortality) was compared between 2 types of anatomic repair (ie, atrial switch plus Rastelli and atrial switch plus arterial switch) and physiologic repair. The study suggests that a Rastelli anatomic repair has the lowest in-hospital mortality, the lowest incidence of postoperative heart block, and a lower incidence of postoperative AV valve regurgitation compared with physiologic repair. In another study, anatomic repair for congenitally corrected transposition of great arteries associated with left ventricular outflow tract obstruction and a VSD were excellent and an overall survival rate of 70% was reported at 20 years in 21 consecutive patients.[44]

  • The other large study (189 patients) found no statistical differences between long-term survival rates (follow up over 30 y for some patients) of patients who underwent conventional surgical repair versus those of patients who underwent anatomic surgical repair.[8] The study reported that results of conventional repair were satisfactory, except in patients with significant tricuspid regurgitation. The recommendation was that anatomic repair should be the procedure of choice for those patients.

Future and Controversies

Although the surgical management of this condition is still evolving, a shift towards anatomic repair is clearly noted. In his review of the surgical literature for this condition, Bove combined reports from 4 studies and obtained an operative mortality rate of 8% (4 deaths in 50 operations) for patients undergoing either combined Senning or Mustard with arterial switch or Rastelli.[5] He noted that associated heart block, ventricular dysfunction, and tricuspid valve regurgitation are all reduced when compared with traditional techniques.

Several centers have demonstrated excellent hospital and midterm survival after double-switch procedures.[45, 46, 47, 29] Langley et al have noted new left ventricular dysfunction and new aortic regurgitation in a few patients late after the double-switch procedure.[46] Continued surveillance of these abnormalities is required.

Whether or not atrial arrhythmias are commonly encountered after the atrial switch operations remains to be determined. The long-term mortality rate after the double-switch operations is still unknown because these have only been proposed in approximately the last decade.[32]