Echocardiography in Pediatric and Adult Congenital Heart Disease, 2nd Ed.

39. Evaluation of the Adult with Transposition after Atrial or Arterial Switch Operations

In the current era, the vast majority of infants born with complete transposition of the great arteries (d-TGA) undergo an arterial switch operation soon after birth. The success of this procedure has obviated the need for the right ventricle (RV) to function as a systemic ventricle. However, the majority of patients operated on before 1985 underwent other procedures that resulted in a lifelong commitment of the RV to function as the systemic pump. It is important for the echocardiographer to appreciate the nuances of these techniques when evaluating long-term outcome of these patients. This chapter will be devoted to the evaluation of the adult with d-TGA after an atrial switch (Mustard or Senning) and will address some of the long-term issues associated with the arterial switch operation (ASO). The long-term results for the ASO have been excellent. The first generation of adult survivors of the ASO have thrived with minimal impact on their lifestyles. However, this group of patients may encounter unique problems related to progressive neoaortic valve regurgitation and neoaortic root dilation. Echocardiography is uniquely suited to evaluate these issues after an ASO.

HISTORICAL PERSPECTIVE

The evolution of the surgical treatment of complete d-TGA is an important and fascinating story of humans’ ingenuity in dealing with a lethal congenital anomaly. Although survival of patients with d-TGA beyond infancy if associated with atrial (ASDs) and/or ventricular septal defects (VSDs) was possible without operation, the majority of patients with d-TGA died in infancy. Those rare infants who survived did so with significant exercise limitation and the morbidity and mortality associated with erythrocythemia and Eisenmenger syndrome. The earliest operation described for d-TGA was the creation of an ASD by Blalock and Hanlon in 1950. This ingenious operation preceded the introduction of the heart-lung machine and was performed on the beating heart. This operation had a relatively high mortality because these infants were very ill and usually quite acidotic. However, it resulted in survival beyond infancy. In 1956, Baffes described a partial repair of d-TGA. The “Baffes” procedure involved connecting the inferior vena cava (IVC) to the left atrium and connecting the right pulmonary veins to the right atrium. Subsequently, Senning (1959) described rerouting of the system and pulmonary venous return that resulted in complete separation of the pulmonary and systemic venous returns. This was accomplished by using right atrial and atrial septal tissue to construct a baffle. In 1964, in a single case report, Mustard described a similar operation using synthetic material that also resulted in complete separation of the pulmonary and system venous returns. However, both atrial switch operations resulted in the RV remaining as the systemic ventricle. Although the “Mustard” operation had the same end result as the “Senning” operation, the former was more popular in the United States. From 1959 to 1975, the Senning and Mustard operations were the mainstay of “physiologic correction” operations for patients with d-TGA and an intact ventricular septum.

In 1975, Jatene and colleagues resurrected the concept of anatomic repair of d-TGA and described a number of successful arterial switch procedures. Since the early 1980s, the arterial switch operation has been the operation of choice for patients with d-TGA with or without VSD but without significant pulmonary valve stenosis. In the current era, the Senning and Mustard operations are rarely performed, usually only for patients who are not candidates for an arterial switch or Rastelli procedure. In the late 1970s and early 1980s, the operative mortality for the Senning and Mustard operations actually was lower than that for the Jatene procedure. However, it was anticipated that the operative mortality for the Jatene procedure would decline significantly as surgeons gained experience with the operation and that the long-term results for the Jatene operation would be superior to those of the Senning and Mustard operations. Time has proved that both of these assumptions are true.

The quest for an operation to replace the Senning or Mustard procedure was spurred on because of the long-term complications inherent to these operations. The complications included superior vena cava (SVC) or IVC obstruction (reported in 15% of patients), pulmonary vein obstruction (reported in 5% of patients), arrhythmias, and right ventricular (systemic ventricle) failure. Systemic ventricular failure and some serious arrhythmias may be amenable only to cardiac transplantation or, very rarely, conversion of the Mustard/Senning to an arterial switch procedure. Cardiac transplantation is costly and is associated with significant mid- and long-term morbidity and mortality. Conversion to an arterial switch usually requires banding of the pulmonary artery to prepare the left ventricle (LV). Both the pulmonary banding procedure and the arterial switch operation in these adult patients are associated with significant mortality and the long-term outcome is poorly understood. The late arterial switch has generally been abandoned in adult patients.

Patients who had an atrial switch operation (Senning or Mustard) operation for d-TGA encounter unique problems as they enter adulthood. Overall, approximately 80% are alive and generally doing well at 20 years postprocedure. Problems in adulthood include atrial arrhythmia (present in greater than 50%), systemic and pulmonary venous baffle obstruction, and deterioration of the systemic RV. Systemic baffle obstruction is more common after the Mustard operation (SVC is more common than IVC). Pulmonary venous baffle obstruction is more common after the Senning operation. These problems can usually be managed in the cardiac catheterization laboratory with intravascular stent placement or during hybrid minimally invasive surgical/intravascular stent placement procedures. Functional assessment of the systemic RV is challenging and fraught with measurement pitfalls and undependable geometric assumptions. Historically, clinicians have depended on a visual “gestalt” of right ventricular systolic function rather than rigorous quantitation of ejection fraction. Newer techniques to assess function may offer previously unavailable quantitation of systemic RV function.

ASSESSMENT OF THE ADULT AFTER ATRIAL SWITCH OPERATION

After atrial switch operation, not all portions of the systemic venous and pulmonary venous pathways can be visualized in one acoustic window. Standard subcostal, parasternal, apical, and suprasternal windows are used to evaluate these pathways after the Mustard or Senning operation. However, since the vast majority of these patients are currently adults, the subcostal window may have limited utility. Gross visual assessment of right ventricular systolic function should be performed from as many of these windows as available in a given patient. Parasternal long- and short-axis images will typically demonstrate a flattened ventricular septum and a “D”-shaped LV, since the RV is the systemic pump (Fig. 39.1 A,B). The tricuspid regurgitation spectral Doppler signal in these patients represents systemic ventricular pressure and does not indicate pulmonary hypertension. In the apical projection, one can assess the pulmonary venous pathway. This pathway is divided by the SVC systemic venous baffle into a posterior chamber that receives the pulmonary veins and an anterior “right atrium” chamber that contains the inlet of the tricuspid valve. The term “pulmonary venous atrium” is used to describe one or both of these chambers after atrial switch operation. The anatomic connection of the pulmonary veins to the native left atrium is not disturbed during an atrial switch procedure. The flow from the pulmonary veins travels anteriorly and laterally over the SVC baffle to access the tricuspid valve. The complexity of the course of the systemic venous baffles and their relationship to the pulmonary venous flow explains why multiple acoustic windows are needed to fully assess these patients.

Figure 39.1. Adult patient after Mustard operation. A: Parasternal long-axis image demonstrating leftward displacement of the ventricular septum due to the systemic right ventricular (RV) dilation. B: Parasternal short-axis image in the same patient demonstrating a “D”-shaped left ventricle (LV) as a result of septal flattening caused by the systemic systolic pressure in the right ventricle. C: Apical four-chamber image demonstrating RV dilation in this patient. Varying severity of RV systolic dysfunction is present in these adult patients. D: Mild tricuspid regurgitation in the same patient. Progressive tricuspid regurgitation may become a problem as RV systolic dysfunction progresses.

The apical four-chamber window provides an excellent assessment of RV dilation and tricuspid regurgitation (Fig. 39.1C,D). In addition, the pulmonary venous and systemic venous baffles can be assessed from this window. If one begins the scan tilted slightly posterior, the pulmonary venous pathway is readily visualized in most patients (Fig. 39.2). Tilting just anteriorly from the pulmonary venous baffle (returning to a true four-chamber view), so that the mitral valve leaflets are visualized, permits assessment of the IVC portion of the systemic venous baffle (Fig. 39.3). Remembering that the apical four-chamber image is oriented in a posterior plane from superior to apical, the IVC baffle is visualized when the mitral leaflets are seen. Conversely, if one rotates clockwise and tilts slightly anterior into an LV outflow tract view, then sometimes the SVC portion of the systemic venous baffle may come into view. The SVC baffle is best evaluated from the parasternal long-axis projection with medial tilt of the transducer (Fig. 39.4). The portion of the pulmonary venous pathway that is posterior to the SVC baffle can also be evaluated in this imaging plane. If an SVC baffle obstruction is present, the suprasternal notch or high right parasternal views may be helpful to obtain a gradient.

Echocardiography plays an important role in the evaluation of systemic and pulmonary venous baffle obstructions in patients after the atrial switch operation. Pulmonary venous pathway obstruction can be detected from the apical four-chamber window (Fig. 39.5). Figure 39.6 demonstrates an adult who had successful resolution of IVC baffle obstruction with placement of an intravascular stent. The IVC baffle stent is well visualized in the apical four-chamber projection (see Fig. 39.6 A,B). Conversely, relieving pulmonary venous baffle obstruction is technically very challenging in the interventional cardiac catheterization laboratory. Either a transseptal or retrograde aortic approach is needed to access the area of pulmonary venous pathway stenosis. Frequently, stent placement in this region is quite difficult due to the circuitous course of the delivery sheath. Newer hybrid techniques using minimally invasive surgical approaches offer much promise for these patients (Figs. 39.7 and 39.8).

Residual atrial level shunts occur rarely in atrial switch patients and these shunts are usually small. Color Doppler assessment of the pulmonary and systemic venous pathways can demonstrate these shunts. However, since no true atrial septum is present in these patients, the residual shunts, if small, may not be readily apparent with surface echocardiography. Dynamic left ventricular (pulmonary ventricle) outflow obstruction may occur in postoperative atrial switch patients. The obstruction is frequently due to subvalvular fibromuscular obstruction, but valvular pulmonary stenosis also occurs. The morphologic LV is designed inherently to be a high-pressure pump and usually tolerates the left ventricular outflow tract (LVOT) obstruction without significant consequence. Any gradient across the LVOT can usually be evaluated from the apical window when one rotates clockwise into an outflow projection. A small portion of patients who had a late (after 1 year of age) atrial switch or an associated VSD may have pulmonary vascular obstructive disease in adulthood. In these patients, the mitral valve regurgitation signal is useful to evaluate pulmonary ventricle systolic pressure. If left ventricular systolic pressure is elevated, one needs to ensure that LVOT or pulmonary venous pathway obstruction is not present.

Figure 39.2. Pulmonary venous pathway after atrial switch operation in d-TGA. Left: Pathologic specimen cut to demonstrate the pulmonary venous pathway (PV) after atrial switch operation. A small portion of the systemic venous baffle (arrow) is demonstrated just above the mitral valve. Middle:Apical four-chamber image demonstrating similar anatomy. SV, systemic venous baffle. Right: Color Doppler demonstrates laminar flow from the pulmonary veins to the right atrium. LV, left ventricle; RV, right ventricle.

Figure 39.3. Systemic venous pathway (IVC) after atrial switch procedure in d-TGA. A: Tilting into a true apical four-chamber view from the more posterior pulmonary venous pathway (PV) (left), one can now adequately assess the inferior vena cava (IVC) portion of the systemic venous baffle (right).The superior vena cava portion of the systemic venous baffle is not easily visualized in the four-chamber projection. Sometimes the SVC baffle can be partially visualized if one rotates clockwise and tilts anteriorly into the left ventricular outflow tract (LVOT) view. B: Three-dimensional images from the apical four-chamber projection demonstrate the PV (right) and the IVC baffle (left). The relative positions of the right atrium (hash) and left atrium (asterisk) are noted in each panel. LV, left ventricle; RV, right ventricle; IVC, inferior vena cava.

Figure 39.4. Parasternal long-axis image demonstrating the superior vena cava (asterisk) portion of the systemic venous baffle as it enters the left atrium (LA). A portion of the pulmonary venous pathway (PV) is also visualized in this image. LV, left ventricle; RV, right ventricle; PV, pulmonary venous baffle.

NOVEL TECHNIQUES FOR THE FUNCTIONAL ASSESSMENT OF THE SYSTEMIC RIGHT VENTRICLE

Both the anatomic structure and the physiologic demands of the normal RV and LV are significantly different. Right ventricular chamber geometry is complex with both inlet (sinus) and outlet (conus or infundibulum) components and a contraction pattern that favors longitudinal over radial shortening. Despite the presence of equal right and left ventricular cardiac outputs in the normal circulation, right ventricular physiology is also quite distinct from that of the LV, as these ventricles pump to a very different vascular bed. As a result, a different pressure–volume relationship exists and right ventricular external work is approximately 25% of left ventricular work (Fig. 39.9).

Figure 39.5. Apical four-chamber two-dimensional and color Doppler assessment of a patient after Senning operation with significant pulmonary venous pathway (PV) obstruction (arrow). The proximal systemic venous baffle (SV) is also visualized.

Figure 39.6. Stent placement after a Mustard operation with history of IVC baffle obstruction. A: Posteriorly tilted apical four-chamber image of a stent (arrow) in the inferior vena cava (IVC) baffle. A short-axis view of the proximal stent is visualized in this image. B: When one tilts anteriorly to a true apical image, the stent’s length (arrow) becomes apparent. LV, left ventricle; RV, right ventricle. C: Parasternal long-axis image in the same patient demonstrating the IVC stent (arrow) projecting into the systemic venous atrium. A portion of the superior vena cava baffle (asterisk) is also visualized in this image.

Figure 39.7. After a Senning operation, this patient developed pulmonary hypertension due to pulmonary venous pathway obstruction. A: Two-dimensional image from the apical four-chamber projection while tilting the transducer posteriorly. The obstruction is clearly identified measuring less than 1 cm. LV, left ventricle; RV, right ventricle. B: Magnetic resonance images in the same patient identifying the obstruction (arrow) between the pulmonary venous (PV) portion of the pathway and the native right atrium (RA). C: Continuous-wave Doppler assessment of the mean gradient (15 mm Hg) across the pulmonary venous pathway obstruction measured in the same projection as in A.

Figure 39.8. Intraoperative transesophageal echocardiographic images performed during a hybrid minimally invasive surgery to place a stent in a pulmonary venous pathway obstruction. A: Two-dimensional image demonstrating severe narrowing (8 mm) of the pathway between the pulmonary venous atrium (PVA) and the native right atrium (RA). BBefore stent placement, continuous-wave Doppler velocity profile demonstrating a mean gradient of 12 mm Hg between the pulmonary venous atrium (PVA) and the native right atrium (RA). C: Two-dimensional image status postplacement of a stentacross the stenosis between the pulmonary venous atrium (PVA) and the native right atrium (RA). Pulmonary venous pathway diameter equals 14 mm with the stent deployed. D: After stent placement, continuous-wave Doppler velocity profile across the pulmonary venous pathway stent. Residual mean gradient equals only 4 mm Hg.

Figure 39.9. Pressure–volume relationship of the normal right and left ventricle. Note that the left ventricle (A) is a “square wave” pump whose filling and ejection patterns differ significantly from those of the right ventricle. Right ventricular (RV) ejection occurs early during ventricular pressure rise and continues beyond the development of peak RV pressure. (B) The relative proportion of left ventricular versus RV work is calculated by measuring the area of each of these pressure–volume relationships. (From: Redington AN. Right ventricular function. Cardiol Clin. 2002;20:341–349.)

Chronic alterations in ventricular loading conditions impart adverse effects on right ventricular performance in the setting of the systemic RV. While many echocardiographic modalities are available to quantitatively evaluate left ventricular systolic and diastolic function, a much more limited armamentarium exists to similarly evaluate right ventricular function (Tables 39.1 and 39.2). In fact, in the clinical setting, the most common approach to the echocardiographic evaluation of right ventricular systolic function is a qualitative visual approach. While three-dimensional echocardiography and cardiac magnetic resonance imaging (MRI) offer a reliable quantitative measure of right ventricular volume and ejection fraction, these modalities are not always readily available. However, they do have distinct advantages over two-dimensional and Doppler echocardiographic approaches, particularly in adults with congenital heart disease and limited transthoracic windows.

Traditional measures of right ventricular function such as fractional area change and ejection fraction are limited because of the complex geometry of the RV. Doppler measures of right ventricular inflow and outflow also may provide valuable information on the systolic and diastolic performance of the RV but are significantly influenced by changes in right ventricular filling with respiration. One important Doppler finding, however, that is often helpful in the assessment of right ventricular diastolic function is the presence of antegrade diastolic forward flow into the main pulmonary artery in diastole (Fig. 39.10). Measured with pulsed-wave Doppler distal to the pulmonary valve, this Doppler pattern suggests a “stiff” RV with decreased ventricular compliance. This Doppler pattern may occasionally be present in the normal circulation but is low in velocity (<10 cm/s) and is not typically present throughout the respiratory cycle. In contrast, patients with a restrictive noncompliant RV have a higher Doppler velocity (>20 cm/s) that is characteristically present throughout the respiratory cycle.

Additional Doppler measures have been clinically useful to evaluate global and longitudinal right ventricular function in the setting of congenital heart disease with a systemic RV. The myocardial performance index (MPI) incorporates both systolic and diastolic components of right ventricular function and has been shown to be a valuable clinical parameter to serially follow in these patients. Similarly, tricuspid annular plane systolic excursion (TAPSE) and tissue Doppler imaging (TDI) have provided valuable insights into longitudinal right ventricular performance in patients with congenital heart disease. In particular, isovolumic acceleration (IVA) has been shown to be a clinically robust measure of right ventricular contractile function that is relatively independent of loading conditions. These more novel Doppler measurements, however, are limited by their angle dependence as well as the impact of cardiac motion and tethering on these velocities.

Recent developments in imaging technology now enable the echocardiographic evaluation of regional myocardial function as well as myocardial twist and torsion with strain and strain rate imaging. Clinical studies in patients with congenitally corrected transposition of the great arteries (CC-TGA) have demonstrated decreased right ventricular global strain and strain rate in a small number of patients with qualitatively normal right ventricular systolic function (Fig. 39.11). A recent study in asymptomatic patients with d-TGA after Senning repair demonstrated distinct changes in right ventricular mechanics and performance in this cohort. Interestingly, the systemic RV had a deformation pattern more similar to the normal LV rather than the normal RV with a shift from longitudinal to circumferential shortening (Fig. 39.12). In addition, there was an almost complete absence of both rotation and global torsion in these systemic RVs (Fig. 39.13). While some changes in the systemic RV appeared to be “adaptive” to the chronic alteration in ventricular load, the lack of myocardial rotation and torsion, coupled with decreases in systolic strain and strain rate, suggests the presence of myocardial dysfunction in these apparently “normally” functioning ventricles. Ongoing functional evaluation with these novel echocardiographic modalities as well as cardiac MRI will continue to offer additional important insights into ventricular mechanics in patients with a systemic RV.

Figure 39.10. Restrictive right ventricular (RV) filling in postoperative tetralogy of Fallot. Parasternal short-axis scan with pulsed-wave Doppler interrogation in the main pulmonary artery. Note the antegrade forward flow (arrow) into the pulmonary artery with atrial contraction. This Doppler pattern is consistent with decreased RV compliance.

LONG-TERM ISSUES FOR THE ADULT AFTER ARTERIAL SWITCH OPERATION

In the mid-1980s the arterial switch operation (ASO) became the “standard of care” for neonates with complete transposition of the great arteries. From 1985 through 2000 a gradual decline in operative mortality occurred. In the 1980s, operative mortality was high at approximately 25%. It has improved in the 2000s but still remains a concern. Brown and colleagues from Indiana University have reported that in a large single center experience operative mortality for the ASO was still between 1% and 2%.

Figure 39.11. Evaluation of systemic right ventricular (RV) performance in patients with congenitally corrected transposition of the great arteries (CC-TGA). Note the decreased systolic strain and strain rate in CC-TGA patients compared with control subjects. In addition, an increased RV myocardial performance index and decreased tissue Doppler displacement are consistent with impaired RV function in this cohort. (From: Bos JM, Hagler DJ, Silvilairat S, et al. Right ventricular function in asymptomatic individuals with a systemic right ventricle. J Am Soc Echocardiogr. 2006;19:1033–1037.)

Figure 39.12. Right ventricular (RV) strain in the normal right and left ventricles and in patients with transposition of the great arteries (d-TGA). Note the significant change in the strain pattern in the systemic right ventricle to one more similar to a normal left ventricle versus the normal RV pattern of deformation. (From Pettersen E, Helle-Valle T, Edvardsen T, et al. Contraction pattern of the systemic right ventricle. J Am Coll Cardiol. 2007;49:2450–2456.)

Figure 39.13. Ventricular rotation in the normal left ventricle (LV) and the systemic right ventricle (RV). The normal LV has clockwise basal rotation and counterclockwise apical rotation that result in ventricular torsion. Note the absence of basal and apical rotation in the systemic RV, resulting in absence of ventricular torsion in this cohort. (From Pettersen E, Helle-Valle T, Edvardsen T, et al. Contraction pattern of the systemic right ventricle. J Am Coll Cardiol. 2007;49:2450–2456.)

Children who had an ASO are now entering adulthood. The vast majority of these patients live normal active lifestyles. Left ventricular function is generally excellent. This is in contradistinction to the patients who had an atrial switch operation where the fate of the systemic right ventricle remains a perplexing problem throughout their lives. Lifestyle issues for adults who had an ASO in infancy include: sports participation, the need in some for lifelong endocarditis prophylaxis, and concerns regarding pregnancies. To date data are sparse to guide decisions on these issues. In the current era, neurodevelopmental outcomes have become very important. Several studies have shown that despite successful neonatal cardiac surgery, many survivors with congenital heart disease face cognitive problems as they reach adulthood. One study from France noted that the prenatal diagnosis of transposition of the great arteries resulted in improved neurocognitive outcome when compared to infants who were diagnosed postnatally.

Reybrouck and colleagues from Belgium compared patients who had an ASO versus those who had an atrial switch operation versus a control group of normal individuals. They noted that aerobic exercise function and efficiency of pulmonary gas exchange were approximately equal for normal controls and patients after ASO. Both of these groups exceeded the performance of patients who have had an atrial switch operation. In one of the largest follow-up studies, evaluating 1095 patients after ASO, Losay and colleagues found that 15 years after ASO late mortality was low. There were no deaths five years postoperatively. Reoperations in this group were mainly due to pulmonary valve issues and branch pulmonary artery stenosis. They found that aortic valve regurgitation and coronary obstruction were rare. Fifteen-year survival in this group was 88% and freedom from reintervention was 82%. Nine percent of patients in this study had moderate or more aortic regurgitation at 15 years postoperatively. Normal left ventricular systolic function and sinus rhythm were present in over 96% of these patients during this 15-year follow-up period. The ACC/AHA 2008 guidelines for management of adults with congenital heart disease list the following as Class I indications for surgical reintervention after ASO (Level of Evidence = C):

1.RVOT obstruction (peak gradient >50 mm Hg or right ventricular systolic pressure >70% systemic). Lesser degrees of obstruction if pregnancy is planned or the patient is exhibiting exercise intolerance or if there is severe pulmonary valve regurgitation.

2.Coronary artery abnormalities with myocardial ischemia not amenable to percutaneous intervention.

3.Severe neoaortic valve regurgitation.

4.Severe aortic root dilation (>55 mm); however, the authors did stipulate that this recommendation is based on no data related to patients who had an ASO and is borrowed from degenerative aortic root disease. The applicability of this recommendation to these patients is therefore uncertain.

Figure 39.14. Dyne-CT image obtained in the congenital cardiac catheterization laboratory. Posterior view of the pulmonary arteries in a teenager with a history of an arterial switch operation and LeCompte maneuver. The proximal left pulmonary artery has a “twisting” type of stenosis (arrow) that was not appreciated on the anterior/posterior and straight lateral images. This patient had successful stent implantation and relief of a significant pressure gradient. (Courtesy Nathan Taggart, MD, Mayo Clinic.)

As children who had an ASO enter adulthood, imaging with surface 2D echocardiography may become more challenging. Alterative imaging techniques utilizing MRI or CTA for assessment of coronary patency, and Dyne-CT (Fig. 39.14) for assessment of branch pulmonary artery stenosis are utilized and influence timing of intervention for these patients.

In 2006, a more recent follow-up study from the French group evaluated 1156 hospital survivors after ASO. Aortic regurgitation was present in 30% of these individuals at 15 years postoperatively. However, only 1.4% required reoperation for aortic regurgitation. The following factors were identified in that study as increasing the risk for development of severe aortic regurgitation after ASO:

■VSD

■Older age at time of ASO

■Prior pulmonary artery banding

■Pulmonary artery/aortic size mismatch

■Coronary anomalies that required large buttons

For those patients who require reoperation for aortic valve intervention or for neoaortic root replacement after ASO the technical aspects of the procedure are not straightforward. The orientation of the great arteries in these patients is still parallel, not orthogonal (as in the normal heart; Fig. 39.15). This creates technical issues for the surgeon. In addition, the majority of these patients have had a LeCompte maneuver performed during the neonatal ASO and the pulmonary arteries are draped anteriorly over the neoaortic root (Fig. 39.16). The pulmonary artery will therefore need to be divided in order for the surgeon to gain access to the neoaortic root.

Figure 39.15. CT image from an oblique sagittal projection in a 23-year-old with a history of an arterial switch operation for d-transposition. Note the dilated neoaortic root and the vertical orientation of the aorta, consistent with parallel orientation of the great arteries in d-transposition. She had successful valve-sparing, neoaortic root replacement. The indication for surgery was progressive root dilation and new onset aortic valve regurgitation.

Risk factors for development of neoaortic root dilation after ASO are similar to those for neoaortic valve regurgitation, namely: VSD, prior pulmonary artery banding, older age at time of arterial switch operation, and coronary artery anomalies that required large buttons. The largest North American study that evaluated long-term follow-up after ASO is a combination of the Toronto and Boston experiences (n= 335 patients). This study demonstrated that, at 10 years postoperatively, neoaortic root dilation was present in half of patients. Seven percent had moderate or greater aortic valve regurgitation, and 5% required either root or valve surgery at 10 years after the ASO.

Few data are available regarding pregnancy outcomes in women with transposition after ASO. The combined Toronto/Boston experience included only nine women who had 17 pregnancies. There were no maternal deaths. Two women had cardiac complications.

Figure 39.16. Another CT image from the same patient described in Figure 39.15. Note the orientation of the pulmonary artery, after the LeCompte, as it drapes anteriorly over the dilated aortic root. The pulmonary artery needed to be transected and then repaired in order for the surgeon to perform a successful neoaortic root replacement.

CONCLUSIONS/SPECULATION FOR THE ADULT AFTER ARTERIAL SWITCH

It is tempting to call the ASO a “cure” but this is not true and these patients require lifelong surveillance for development of premature coronary artery disease, progression of neoaortic valve regurgitation, and progression of neoaortic root dilation. Most of these patients live unrestricted lifestyles with no sports or activity restrictions and no need for ongoing endocarditis prophylaxis. Periodic exercise testing for evaluation of premature coronary artery disease with stress echo or nuclear treadmill testing is recommended. Generally most women after ASO are candidates for pregnancy. But they should have a thorough evaluation at a center specializing in the care of adult congenital heart patients prior to contemplating pregnancy. Branch pulmonary artery stenoses continue to be largely managed with balloon angioplasty and stent placement. The major issue for the next decade will be the durability of the neoaortic valve beyond 20 years postoperatively. This reinforces the need for lifelong surveillance of these patients, and echocardiography is uniquely suited for long-term evaluation after ASO.

SUGGESTED READING

Baffes TJ. A new method for surgical correction of transposition of the aorta and pulmonary artery. Surg Gynec Obstet. 1956;102:227.

Blalock A, Hanlon C. The surgical treatment of complete transposition of the aorta and the pulmonary artery. Surg Gynecol Obstet. 1950;90:1.

Bos JM, Hagler DJ, Silvilairat S, et al. Right ventricular function in asymptomatic individuals with a systemic right ventricle. J Am Soc Echocardiogr. 2006;19:1033–1037.

Brown JW, Park HJ, Turrentine MW. Arterial switch operation: Factors impacting survival in the current era. Ann Thorac Surg. 2001;71:1978–1984.

Ebenroth ES, Hurwitz RA. Long-term functional outcome of patients following the Mustard procedure. Congenit Heart Dis. 2007;2:235–241.

Jatene A, Fontes V, Paulista P, et al. Successful anatomic correction of transposition of the great vessels: a preliminary report. ARQ Bras Cardiol. 1975;28:461–464.

Losay J, Touchot A, Capderou A, et al. Aortic valve regurgitation after arterial switch operation for transposition of the great arteries. J Am Coll Cardiol. 2006;47:2057–2062.

Losay J, Touchot A, Serraf A, et al. Late outcome after arterial switch operation for transposition of the great arteries. Circulation. 2001 Sep18;104(12 Suppl 1):I-121–126.

Mustard WT. Successful two-stage correction of transposition of the great vessels. Surgery. 1964;55:469–472.

Pettersen E, Helle-Valle T, Edvardsen T, et al. Contraction pattern of the systemic right ventricle. J Am Coll Cardiol. 2007;49:2450–2456.

Redington AN. Right ventricular function. Cardiol Clin. 2002;20:341–349.

Senning A. Surgical correction of transposition of the great arteries. Surgery. 1959;45:966.

Questions

1.The pulmonary venous baffle in a patient who had a Mustard operation is best visualized in which of the following imaging planes?

A.Parasternal short axis

B.Suprasternal notch

C.Subcostal sagittal

D.Apical four chamber

2.In a patient with complete transposition of the great arteries who had a Senning operation, which of the following problems is likely?

A.Frequent runs of ventricular tachycardia

B.Need for pacemaker placement

C.Pulmonary hypertension

D.Development of protein losing enteropathy

3.Which of the following operations uses the largest amount of prosthetic/synthetic material?

A.Mustard

B.Senning

C.Arterial switch

D.LeCompte maneuver

4.In a patient who had a Mustard operation, which of the following baffle stenoses is most common?

A.SVC baffle stenosis

B.IVC baffle stenosis

C.Pulmonary venous baffle stenosis

D.Coronary sinus baffle stenosis

5.In a patient with complete transposition of the great arteries who had a Senning operation, which of the following Doppler signals is most reliable for determination of left ventricular systolic pressure?

A.Mitral regurgitation

B.Tricuspid regurgitation

C.Aortic regurgitation

D.Pulmonary regurgitation

6.In a patient with complete transposition of the great arteries the parasternal long-axis image will demonstrate which of the following?

A.Discontinuity between the semi-lunar valve and the mitral valve

B.Connection of the left atrium to the right ventricle

C.Parallel orientation of the semi-lunar valves

D.Enlargement of the left ventricle

7.After the arterial switch operation, which of the following becomes a more frequent problem as these patients age?

A.Need for AV sequential pacemaker placement

B.Superior vena cava stent placement

C.Neoaortic valve regurgitation

D.Branch pulmonary artery aneurysm formation

8.Which of the following risk factors has NOT been associated with progressive neoaortic valve regurgitation in patients after an arterial switch operation (ASO)?

A.VSD

B.Prior pulmonary artery band

C.Coronary anomalies requiring large buttons

D.ASO within the first week of life

9.The 2007 ACC/AHA guidelines for the management of adults with congenital heart disease list which of the following as a Class I indication for surgical reintervention?

A.RVOT obstruction with a peak gradient of 30 mm Hg

B.Moderate neoaortic valve regurgitation

C.Sinus of Valsalva measurement of 45 mm

D.Right ventricular systolic pressure = 80% of systemic systolic pressure

10.Which of the following operations for complete transposition of the great arteries has been associated with the lowest reoperation rate:

A.Mustard

B.Senning

C.Rastelli

D.Arterial switch

Answers

1.Answer: D. The apical four-chamber image clearly demonstrates the pulmonary venous baffle in patients after a Mustard or Senning operation. Pulmonary baffle stenosis can be readily identified in this view.

2.Answer: B. After the Senning and Mustard operations it is common for adult patients to require placement of pacemakers. The leads from these pacemakers will be readily identified in the superior vena cava baffle, as well as the native left atrium and left ventricle. These leads will appear posterior on a lateral chest x-ray image identifying that this is a patient who had an atrial switch operation.

3.Answer: A. In 1964, Mustard described an operation similar to what Senning had previously described using native tissue, however Mustard used synthetic material to completely separate the pulmonary and systemic venous pathways.

4.Answer: A. After a Mustard operation, systemic venous baffle stenoses are more common than pulmonary venous baffle stenoses (in contradistinction to the Senning operation). After a Mustard operation, the superior vena cava baffle tends to be obstructed more commonly than the inferior vena cava baffle. This is partially due to construction of the baffle. In addition, placement of pacing leads across this baffle may exacerbate narrowing.

5.Answer: A. After an atrial switch operation, the left ventricle still pumps to the pulmonary artery. The mitral regurgitation signal, if present, is a reliable estimate of left ventricular systolic pressure. Pulmonary and subpulmonary stenosis is not an uncommon finding in these patients, so this signal does not necessary reflect pulmonary artery systolic pressure.

6.Answer: C. The parasternal long- axis image demonstrates parallel orientation of the semi-lunar valves and the great arteries in complete transposition of the great arteries. The pulmonary valve (posterior semi-lunar valve) is in fibrous continuity with the mitral valve since they are both connected to a morphologic left ventricle.

7.Answer: C. As patients who had an ASO are followed into adulthood, surveillance for progression of neoaortic valve regurgitation is essential. Fortunately < 10% of patients have needed reoperation for this indication. Echocardiography is uniquely suited for the follow-up of these patients.

8.Answer: D. Older age at the time of ASO is associated with more frequent long-term neoaortic valve regurgitation. All of the risk factors may be related to issues that may cause progressive aortic root dilation and lack of support beneath the semilunar valve.

9.Answer: D. Class I indications for surgical reintervention after ASO include the following:

1.RVOT obstruction (peak gradient > 50 mm Hg or right ventricular systolic pressure > 70% systemic). Lesser degrees of obstruction if pregnancy is planned or the patient is exhibiting exercise intolerance or if there is severe pulmonary valve regurgitation.

2.Coronary artery abnormalities with myocardial ischemia not amenable to percutaneous intervention.

3.Severe neoaortic valve regurgitation.

4.Severe aortic root dilation (> 55 mm)

10.Answer: D. The arterial switch operation has allowed greater than 95% of patients to have excellent left ventricular systolic function and sinus rhythm, obviating the need for many reinterventions that are associated with atrial switch and Rastelli-type procedures.