Evaluation and management of the adult patient with transposition of the great arteries following atrial-level (Senning or Mustard) repair
Barry A Love*, Davendra Mehta and Valentin F Fuster About the authors
Correspondence *Congenital Cardiac Catheterization Laboratory, Mount Sinai Medical Center, Box 1201, 1 Gustave L Levy Place, New York, NY 10029, USA
Email barry.love@mssm.edu
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Learning objectives
Upon completion of this activity, participants should be able to:
- Describe the epidemiology and anatomy of transposition of the great arteries (TGA).
- Identify the prognosis after atrial-level repair of TGA.
- Specify physical and other diagnostic findings common after atrial-level repair of TGA.
- List effective treatment strategies for complications after atrial-level repair of TGA.
Competing interests
The authors and the Journal Editor H Camm declared no competing interests. The CME questions author CP Vega declared that he has served as an advisor or consultant to Novartis, Inc.
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Summary
Atrial-level repair for transposition of the great arteries is one of the greatest achievements of modern cardiovascular medicine, transforming a once fatal congenital heart condition into one with excellent long-term survival. Although atrial-level repair has been supplanted by the arterial switch, there remains a population of patients who underwent atrial-level repair as children and now require ongoing care as adults. Survival slowly continues to decline in this population mainly owing to systemic right ventricular dysfunction and sudden death. Other problems include sinus node dysfunction, atrial arrhythmias, systemic atrioventricular valve regurgitation, baffle problems, and pulmonary hypertension. Evaluation and management of these late complications is addressed.
Review criteria
A search for original articles published between 1966 and 2007and focusing on transposition of the great arteries post atrial-level repair was performed in MEDLINE and PubMed. The search terms used were "transposition of the great arteries", "Mustard", "Senning", "arrhythmia" and "pregnancy". All papers identified were English-language, full-text papers. We also searched the reference lists of identified articles for further papers.
Introduction
Transposition of the great arteries (TGA) is a common but serious congenital heart malformation, with an incidence of about 1 per 5,000 live births.1 Until the late 1950s, this lesion was uniformly fatal, with most infants dying before the age of 1 year.2 The development of the Senning and Mustard atrial-level repairs, however, led to good immediate outcomes and long-term survival. By the 1980s, late complications of these repairs had become well recognized and this, combined with advances in infant cardiac surgery led to the adoption of the neonatal arterial switch procedure, which is now standard therapy for transposition. We estimate there to be approximately 9,000 patients in the US currently alive with an atrial-level repair.3 Cardiologists caring for these patients need to understand the anatomy of the repair and the potential late complications associated with it, and be aware of the appropriate therapies. We discuss these issues in this Review.
Anatomy and physiology of transposition of the great arteries
In typical TGA, the atria and ventricles are in the usual position, but the aorta arises anteriorly from the right ventricle and the pulmonary artery arises posteriorly from the left ventricle (Figure 1). This type of transposition is also termed d-TGA for dextro or right because the cardiac looping is usual with the right ventricle to the right of the left ventricle (in contrast to L-TGA often called 'corrected transposition', a completely different disease that will not be discussed here). In patients with d-TGA, desaturated systemic blood returning from the body recirculates to the body and oxygenated pulmonary venous blood recirculates to the lungs, resulting in severe cyanosis from birth. Survival in the neonatal period depends on the two circulations mixing to some degree. A native atrial septal defect or an iatrogenic septal defect (created surgically or with a transcatheter balloon) allows for mixing of the two circulations.
Figure 1 Diagram of typical transposition of the great arteries.
The atria and ventricles are in their usual position, but the aorta arises anteriorly from the right ventricle and the pulmonary artery arises posteriorly from the left ventricle. This diagram also illustrates the additional abnormality of a ventricular septal defect.
Full figure and legend (24K)Figures & Tables indexDownload Power Point slide (230K)Among patients with TGA, three-quarters have no other cardiac lesions and are classified as having simple transposition. The other quarter have one or more additional defects including: ventricular septal defect (16%), pulmonary stenosis (9%), and coarctation of the aorta (4%).3 The presence of other cardiac lesions constitutes complex transposition. Patients with complex transposition have worse early and late outcomes than those with simple transposition.
History of palliation and repair
Surgical intervention for TGA predates the invention of cardiopulmonary bypass. In 1950, Blalock and Hanlon described the first palliative procedure to surgically excise the atrial septum, thereby improving mixing and arterial saturation. With early bypass techniques, Senning performed the first 'complete' repair for TGA in 1957.4 In the Senning repair, a baffle is created within the atria that redirects the deoxygenated caval blood to the mitral valve and the oxygenated pulmonary venous blood to the tricuspid valve (Figure 2). The anatomic left ventricle continues to act as the pulmonary pump and the anatomic right ventricle acts as the systemic pump. In Senning's operation, complicated 'origami-style' cutting and folding of the native atrial tissue is required to achieve the venous baffle. Owing to its complexity, the Senning technique was initially not widely embraced. In 1964, Mustard described a simpler technique by which the atrial septum is excised, and the atrial baffle is created by the placement of a single pantaloon-shaped patch (Figure 3).5 This technique was quickly adopted by surgeons and became the standard operation for TGA.6 One might wonder why the arterial switch procedure was not the technique first employed for TGA? In fact, both Senning and Mustard tried this approach in the early 1950s without success.5, 7 The obstacles to success in that era included the inability to transfer the coronary arteries, and inadequate early techniques of cardiopulmonary bypass that precluded surgery in early infancy.
Figure 2 Diagram of atrial-level repair for transposition of the great arteries.
Both the Mustard and Senning repairs create a baffle within the atria that redirects the caval blood to the mitral valve and the pulmonary venous blood to the tricuspid valve.
Full figure and legend (23K)Figures & Tables indexDownload Power Point slide (228K)Figure 3 The original description of the Mustard technique (surgeon's view).
(A) The patient is placed on cardiopulmonary bypass and the right atrium is opened. The atrial septum is excised, exposing the pulmonary veins, which are now visualized through the atrial septal defect. (B) A pantaloon-shaped patch is fashioned from autologous pericardium. Attachment of the surgical patch is begun to the left of the entrance of the left pulmonary veins. (C) The pantaloon baffle attachment is completed directing the pulmonary venous blood to the tricuspid valve, and directing the superior and inferior vena caval blood to the mitral valve. Mustard WT (1964) Successful two-stage correction of the transposition of the great vessels. Surgery 55: 469–472.
Full figure and legend (30K)Figures & Tables indexDownload Power Point slide (234K)In the early era, many neonates succumbed to cyanosis before any operation. In 1966, Rashkind and Miller pioneered the first interventional catheterization technique to create a large atrial defect, by tearing the thin atrial septum primum with a balloon catheter.8 This procedure enabled palliation for at least 1 year until a definitive operation (Mustard or Senning) could be performed.
The Senning procedure was revived by many surgeons in the mid-1970s.9 The experience that had been gained with atrial baffling in the Mustard procedure enabled many of the technical barriers to be overcome. In addition, the absence of foreign patch material was thought to decrease the incidence of baffle obstruction with somatic growth. Use of the Mustard procedure also continued in many centers. Surgical advances resulted in atrial-level repairs being performed in increasingly younger infants, with 1-year survival rising to more than 90% by the early 1980s.10 Troubling late sequelae of atrial-level repairs were, however, becoming increasingly apparent, including atrial arrhythmias, baffle obstructions, and systemic right ventricular dysfunction, leading to a late decline in survival.10 Concomitant advances led to the introduction of the neonatal arterial switch procedure in the mid-1980s.11 Although the arterial switch had a steep learning curve, by the early 1990s the initial surgical mortality of the arterial switch was similar to that of atrial-level repairs and the latter procedure was virtually abandoned for the treatment of d-TGA. The Senning and Mustard surgeries still have a small role in the treatment of d-TGA in patients with fixed subpulmonary obstruction and as part of the 'double-switch' type of repair used in the treatment of congenitally corrected transposition.
Survival and functional status after atrial-level repair
Several studies have examined the long-term outcomes of patients with Mustard and Senning repairs. For patients who survived to hospital discharge, late survival is 84–95% at 10 years, and 76–89% at 15–20 years.7, 12, 13, 14, 15 The absolute survival is difficult to compare across series as some exclude higher-risk groups. A steady actuarial decline in survival of approximately 0.5% per year does, however, seem to be consistently reported (Figure 4). Patients with complex transposition tend to fare worse in terms of both early and late mortality than patients with simple transposition,12, 13 but most adults with atrial-level repairs seem to fare well. Studies report that 90–95% of patients are in NYHA class I or II.7, 12 Only a small proportion of patients have major neurologic deficits12 and almost all survivors are able to work and function normally in society.7
Figure 4 Late survival for transposition of the great arteries following atrial-level repair.
Survival is assessed from hospital discharge. Data from references 11–15 were used for this analysis.
Full figure and legend (12K)Figures & Tables indexDownload Power Point slide (216K)Late complications of atrial-level repairs
Despite the overall good outcomes after atrial-level repairs, various complications that are symptomatic, that influence long-term prognosis, or both, can affect these patients. Some of these complications are more common in patients who underwent a particular type of atrial-level repair, whereas others seem to be independent of the initial choice of atrial baffle.
Arrhythmia
Sinus node dysfunction
Sinus node dysfunction affects a large proportion of adult patients after atrial-level repair; sinus rhythm is maintained in only 40–50% of patients with Mustard repairs 15–20 years after surgery.7, 16 Patients with Senning repairs have a somewhat lower incidence of sinus node dysfunction.16 The probable mechanisms underlying this complication are damage to the sinus node artery during surgery or progressive fibrosis of the sinus node due to surgical scar lines in this region. Patients with sinus node dysfunction are usually in a junctional escape rhythm and often have a limited ability to increase heart rate with activity. Patients with this complication are at increased risk of atrial arrhythmias and late mortality.7, 17
Atrial flutter
The occurrence of atrial flutter, also called intra-atrial re-entrant tachycardia, seems to increase with time and parallels the development of systemic ventricular dysfunction in many patients.18 At 20 years after surgery, about a third of patients will have experienced at least one episode of atrial flutter.19 The scar lines across the atrium and the suture line along the anatomic isthmus seem to provide the substrate for sustaining atrial flutter. This arrhythmia is frequently exacerbated by sinus node dysfunction, which creates the potential for slow–fast cycles that often trigger re-entry.20
Sudden death
About half of deaths after either type of atrial-level repair are sudden, presumably arrhythmic, deaths.15 Rapidly conducting atrial flutter or primary ventricular arrhythmias are the probable mechanisms.21 Risk factors for sudden death include a history of concomitant ventricular septal defect, atrial flutter, and worsening degrees of systemic right ventricular dysfunction, especially in the presence of heart failure symptoms.18, 19, 22 An important additional risk factor is the presence of pulmonary hypertension.23 Recent work has implicated increased QT dispersion as a risk factor.24
Systemic right ventricular dysfunction
The causes of impaired systemic right ventricular function are not known. One postulated theory is that the triangular geometry of the right ventricle is less-well suited to sustaining the systemic workload than is the bullet-shaped left ventricle. Another theory is that the right ventricle is not 'designed' to pump against systemic afterload. Certainly the myocardial fiber orientation in the right ventricle is different to that in the left ventricle. Suboptimum myocardial protection during cardiopulmonary bypass, especially in the early experience, may also be a contributing factor. It has been shown that the degree of hypertrophy correlates with the degree of ventricular dysfunction.25 In addition, chronic ischemia might have a part in the development of this complication as the metabolic requirements of the hypertrophied systemic right ventricle may outstrip the coronary reserve of this ventricle.26
The ultimate fate of the systemic right ventricle for the majority of patients with atrial-level repairs is uncertain. In clinically asymptomatic patients, ventricular function declines in some but not in others.27, 28 Although patients with asymptomatic systemic right ventricular dysfunction can do well for a long period of time, patients with symptomatic heart failure fare poorly.21
Systemic atrioventricular valve regurgitation
The systemic atrioventricular valve in patients with atrial-level repairs is the anatomic tricuspid valve, which frequently becomes progressively incompetent. Abnormal septal configuration could contribute to tricuspid regurgitation in patients with these repairs as the ventricular septum bows from the high-pressure right ventricle towards the low-pressure left ventricle, 'pulling' the septal leaflet away and leading to a failure of coaptation of the tricuspid valve leaflets (Figure 5).29 This theory is supported by case reports of resolution of even severe tricuspid regurgitation after pulmonary artery banding, which raises the left–right ventricular pressure ratio and restores tricuspid valve septal leaflet apposition;29 however, this restoration is not uniformly observed. Although tricuspid regurgitation is often concordant with worsening degrees of right ventricular function, this relationship is not constant or linear. Why severe tricuspid regurgitation develops in some patients and not in others is unknown.
Figure 5 Transthoracic echocardiogram (parasternal short-axis view) in a patient with transposition of the great arteries following atrial-level repair.
Note the ventricular septum (asterisk) bowing away from the RV towards the LV. Abnormal septal configuration may contribute to tricuspid regurgitation, since the bowed septum pulls the septal leaflet away leading to a failure of coaptation. Abbreviations: LV, left ventricle; RV, right ventricle.
Full figure and legend (22K)Figures & Tables indexDownload Power Point slide (226K)Subpulmonary stenosis
A mild degree of subpulmonary stenosis is common in patients with TGA following atrial-level repair.30 This mild form of subpulmonary stenosis is caused by right-to-left bowing of the ventricular septum in a manner described above. More-severe subpulmonary stenosis, caused by anatomic attachments of the mitral valve to the ventricular septum, or tunnel-like muscular obstruction, is less common.31 In these more-severe forms, pressure in the left ventricle can equal or exceed that of the systemic right ventricle.
Baffle problems
The intra-atrial baffle is vulnerable to leaks and stenoses.7, 12, 14 Although these problems are generally present from a young age, they might not become apparent until adulthood. The systemic venous baffle is estimated to develop stenosis in 5–15% of patients.12, 14 The risk of developing this complication is higher with Mustard repairs than with Senning repairs.19 Both the superior and inferior vena cava baffle limbs can develop stenosis, but the superior vena caval (SVC) baffle limb is more frequently affected (Figure 6). The slowly progressive nature of this obstruction means that clinical SVC syndrome is uncommon, as venous collaterals (especially the azygous vein) enlarge and provide an alternate route for blood from the upper half of the body to return to the heart. Obstruction is sometimes diagnosed when an operator is unable to navigate a pacemaker lead through the superior vena cava. Even clinically silent baffle obstruction can lead to reduced exercise capacity, as venous return (a synonym for cardiac output) is limited.32 Inferior vena caval baffle-limb stenosis is less-well tolerated than SVC baffle-limb stenosis because of the effects of elevated venous pressure on the liver. Patients with inferior vena cava baffle-limb stenosis often present with ascites and hepatomegaly, which should prompt definitive evaluation for this problem.
Figure 6 Superior baffle-limb stenosis in a patient with transposition of the great arteries after atrial-level repair and following implantation of a single-chamber pacemaker.
(A) Injection in the superior vena cava shows the atresia of the superior-vena-cava baffle (arrow) next to the pacemaker lead. A catheter placed from the femoral vein shows the short atretic distance. (B) After radiofrequency wire perforation of the atresia, the area is opened with a stent expanded to 18 mm diameter. (C) Following stent placement, the superior vena-cava injection shows the superior baffle limb to be widely patent. The pacemaker lead was undamaged and was left in place.
Full figure and legend (10K)Figures & Tables indexDownload Power Point slide (214K)Pulmonary venous baffle obstruction is seen more often after the Senning operation than after the Mustard repair.19 The site of obstruction is typically between the inferior vena caval baffle-limb and the lateral atrial wall. Physiologically, this type of obstruction is similar to mitral stenosis in the normal heart. Most atrial-level-repair recipients who reach adulthood with this type of obstruction are asymptomatic at rest, but have a limited capacity for physical activity, as even a mild increase in cardiac output results in a considerable rise in pulmonary venous pressure and pulmonary edema. In patients with pulmonary hypertension, the possibility of pulmonary venous baffle obstruction must be carefully investigated because unlike pulmonary hypertension, it is readily treatable.
Leaks in the intra-atrial baffle are more common with Mustard than with Senning repairs, and typically function as a left-to-right shunt. While a large baffle leak might create a problematic volume load on the pulmonary circuit and atria, small leaks are generally not clinically important. Dependent on the anatomic position of the baffle leak, right-to-left shunting can occur and lead to desaturation, especially with exercise. The combination of a baffle leak proximal to a baffle stenosis will exacerbate right-to-left shunting and worsen resting and exercise oxygen saturation.
Pulmonary hypertension
Infants with TGA, especially those with ventricular septal defects, seem to be at high risk of developing pulmonary hypertension. Among those who do not undergo surgery, 40% of patients with TGA and a ventricular septal defect will develop pulmonary vascular obstructive disease within the first year of life, while 4% of those without a ventricular septal defect will develop pulmonary vascular disease by 1 year.33 With atrial-level repair, the incidence of pulmonary hypertension is reported to be as high as 7%23 but this complication might only become apparent in adulthood. Repair at age older than 1 year seems to be a risk factor.23 In these patients, one surmises that the processes responsible for the cascade of pulmonary vascular obstructive disease were already at an irreversible stage when the atrial-level repair was first performed. In many patients, however, the clinical presentation of pulmonary hypertension is delayed owing to the ability of the pulmonary ventricle (anatomic left ventricle) to pump against a raised resistance. An association might also exist between TGA and a primary form of pulmonary hypertension.34
Endocarditis
While the risk of endocarditis following atrial-level repair for TGA seems to be low, residual ventricular septal defects, subpulmonary stenosis and tricuspid regurgitation, might increase risk. Previously, even in the absence of these lesions, endocarditis prophylaxis was recommended at times of predictable risk throughout life.35 Updated recommendations about endocarditis prophylaxis from the AHA36 and other organizations indicate that patients with atrial-level repair of d-TGA without these higher-risk features are no longer included in the group recommended for prophylaxis. For practical purposes, however, these patients can all be considered to have prosthetic material at the site of the atrial baffle, and most will have at least some degree of tricuspid regurgitation—a high-velocity jet adjacent to the prosthetic material—and so most patients will still fall into the group for whom endocarditis prophylaxis is recommended at times of risk.
Cardiac evaluaton of patients with atrial-level repairs
History, physical examination and appropriate use of selected testing is necessary for proper evaluation of the patient with TGA after atrial-level repair (Table 1). Many adults with congenital heart disease have limited knowledge of their heart disease and heart history.34 It is common to encounter adult patients with TGA that have not seen a physician in many years because they are asymptomatic, have busy young-adult lives, lack medical insurance, or because of a combination of these factors. Every effort should be made to secure past medical records, especially operative and catheterization reports.
Table 1 Suggested evaluation of patients with atrial-level repair of transposition of the great arteries.
Full tableFigures & Tables indexDownload Power Point slide (236K)
History
A complete cardiac history is invaluable to management and should include questioning on the following points: exercise intolerance, particularly if it has developed gradually as it relates to most of the complications above; orthopnea or paroxysmal nocturnal dyspnea, which is unusual but could point to severe pulmonary venous baffle obstruction or pulmonary hypertension; palpitations, which indicate atrial arrhythmias; and syncope, which could be a symptom of atrial or ventricular arrhythmias and necessitates further work up.
Physical examination
Vital signs should be noted, including the resting heart rate—this is often low in patients with sinus node dysfunction. The general appearance of patients is important. Cyanosis is usually absent, but its presence could suggest a baffle leak with stenosis and right-to-left shunt. If the face has a full appearance or the jugular veins are distended, chronic SVC baffle obstruction is the likely cause.
Scars should be evaluated. A midline sternal scar is expected. An additional left thoracotomy scar suggests that a coarctation repair was performed as a staged procedure. If a pacemaker has been implanted a scar will normally be present in the left subclavicular area. If the pacemaker is on the right side, the additional anomaly of a left superior vena cava to coronary sinus should be suspected. A right thoracotomy could indicate that a Blalock–Hanlon atrial septectomy preceded the Mustard or Senning procedure.
The precordium is always dynamic, with a right ventricular heave due to the systemic load in this chamber. The second heart sound is usually single and loud because the aortic valve is just underneath the stethoscope, and the pulmonic component is often not audible. A loud second heart sound does not suggest pulmonary hypertension as it would in a patient with normal anatomy. A holosystolic murmur suggests systemic atrioventricular valve regurgitation or a residual ventricular septal defect, whereas a systolic ejection murmur suggests subpulmonary stenosis.
Hepatomegaly might indicate congestive heart failure, but if other signs are absent, chronic hepatitis should be considered. Many patients were exposed to hepatitis C before the implementation of blood supply screening in the early 1990s.37
Testing
Electrocardiogram
The usual electrocardiographic findings in patients with TGA who have undergone atrial-level repairs show right ventricular hypertrophy (Figure 7). Sinus bradycardia or junctional rhythm and evidence of single-chamber or dual-chamber pacing are frequently seen. If ventricular pacing is present, the stimulated QRS complex demonstrates right-bundle-branch block because the ventricular pacing lead is situated in the left ventricle.
Figure 7 Electrocardiogram in a patient with transposition of the great arteries following atrial-level repair.
Note the resting bradycardia with junctional rhythm alternating with slow sinus rhythm and presence of right ventricular hypertrophy.
Full figure and legend (30K)Figures & Tables indexDownload Power Point slide (234K)Chest radiography
Sternal wires are expected. Right hemidiaphragm elevation might be present as phrenic nerve injury was common in early experiences of the Mustard repair. Cardiomegaly might be seen dependent on the degree of tricuspid regurgitation and systemic right ventricular dysfunction. A pacemaker may be present. The tip of the pacemaker leads will be in the systemic venous atrium and/or the left ventricle.
Echocardiography
Two-dimensional transthoracic echocardiography is invaluable in the management of patients with atrial-level repair. The baffles, atrioventricular valves and subpulmonary area can generally be evaluated.38 Right ventricular function is commonly assessed qualitatively but the reliability of this evaluation is suspect.39 Other echocardiographic methods of quantitative analysis, such as Doppler tissue imaging and myocardial performance index, are worth consideration.40, 41 Unfortunately, poor transthoracic windows frequently preclude complete ultrasonographic evaluation. Transesophageal echocardiography and other imaging modalities are, therefore, complementary.
Cardiac MRI
Cardiac MRI is an excellent noninvasive investigative tool as baffles and ventricular function can be examined in detail.30, 42, 43 Unfortunately, many patients have pacemakers, which currently contraindicates MRI, although this circumstance might change in the future.44
Nuclear medicine
Radionuclide angiography can enable reliable quantitative assessment of the systolic function of the right ventricle. It is a noninvasive test and the results can be used to follow ventricular function over time.42 This method of assessing right ventricular function has fewer technical limitations than MRI or echocardiography but provides limited information.
Exercise testing
Maximum oxygen consumption (VO2max) is blunted among patients with atrial-level repairs, even in those who are asymptomatic.32, 45, 46 This effect probably arises because of a diminished chronotropic response and reduced systemic ventricular performance.
Residual hemodynamic sequelae correlate with reduced VO2max32 and exercise testing is a useful way to screen for these conditions and to monitor functional capacity and hemodynamic status. As many patients are asymptomatic, objective measures over time are important to evaluate subclinical worsening before severe impairment presents.
Cardiac catheterization
Cardiac catheterization remains the gold standard for evaluating the hemodynamic status of patients with atrial-level repairs. The systemic and pulmonary venous baffles can be examined in-detail from both a hemodynamic and an angiographic standpoint, as can the right and left ventricular outflow tracts. In addition, interventional procedures such as baffle dilatation and device occlusion of baffle leaks can be performed. It is worth noting that negotiation of a venous catheter from the left ventricle to the pulmonary arteries is often difficult because the leaflet of the anterior mitral valve directs balloon-tipped catheters to the apex of the left ventricle. A tip-deflecting wire is, therefore, often necessary.
Therapies for complications after atrial-level repairs
Arrhythmia
Bradycardia
Pacing is commonly used as a therapy for sinus node dysfunction.19 More than 20% of patients have a pacemaker, and this incidence is increasing because as those patients with atrial-level repair age, a greater proportion are exhibiting declines in sinus node function.19 Transvenous pacemaker placement is generally the preferred approach, but patency of the SVC baffle limb must be confirmed before the insertion of leads. Baffle leaks should also be identified before lead insertion to prevent inadvertent placement of leads into the systemic circulation. Atrial-rate-responsive pacing is favored, but a dual-chamber pacemaker should be implanted if atrioventricular node function is of concern. The atrial lead is positioned with the tip in the systemic venous atrium. The best atrial-pacing site is usually found within the anatomic left atrial appendage, although healthy atrial tissue can also be found near the superior and inferior vena cava. If the lead is positioned in the left atrial appendage, care should be taken to avoid a site with phrenic nerve stimulation. The ventricular lead is placed in the anatomic left ventricle (Figure 8). The smooth-walled nature of this ventricle means that the lead should be an active-fixation rather than a passive-fixation type.
Figure 8 Chest radiograph of a patient with transposition of the great arteries and atrial-level repair and following implantation of a dual chamber pacemaker.
This patient had atresia of the superior vena cava baffle limb and required stenting before pacemaker placement. Note the stent in the superior vena cava baffle. The atrial lead (A) is positioned within the systemic venous atrium at the site of the anatomic left atrial appendage. The ventricular lead (V) is positioned in the apex of the left ventricle.
Full figure and legend (15K)Figures & Tables indexDownload Power Point slide (219K)Atrial flutter
Therapy for atrial flutter can be medical, electrical or ablative, and these treatments can be administered alone or in combination, as necessary. Ablation techniques have improved substantially over the past decade and the success rate is currently reported to be around 80%.47 The majority of successful ablation sites are at the anatomic isthmus between the inferior vena cava and the tricuspid valve, and are usually approached retrograde through the aortic valve. When performing an ablation in patients with atrial-level repair, the location of the coronary sinus is commonly queried. Anatomically, the coronary sinus follows the course of the mitral annulus, and the ostium is in the usual location in the right atrium near the entrance of the inferior vena cava. With both the Senning and the Mustard procedures, the coronary sinus ostium can be incorporated on either side of the baffle, though usually it is found on the systemic venous side, providing access to this structure for catheter placement. Atrioventricular node/His bundle ablation has been reported in refractory cases of atrial flutter, but this approach is undesirable in patients with systemic right ventricles; in such patients, atrioventricular synchrony is strongly preferable. Medical therapy might be needed if atrial flutter recurs despite one or more ablation attempts, or in patients who do not wish to opt for this treatment. Amiodarone is commonly chosen because of its safety profile in the setting of systemic ventricular dysfunction, however the side effects of this medication, which may need to be administered for many decades, are problematic.19
Simple atrial pacing can decrease the incidence of atrial flutter by reducing the frequency with which an atrial premature beat follows an atrial pause—a pattern that often initiates this arrhythmia. Some pacemakers have algorithms to further reduce these long–short cycles by preferentially pacing the atrium above the sinus rate and briefly increasing the pacing rate following a premature atrial beat. These modes have not been studied prospectively in patients with atrial-level repair. In addition, atrial pacing can enable the use of antiarrhythmics otherwise precluded because of bradycardia. Antitachycardia pacemakers have been used with some success. These pacemakers detect atrial tachycardia and use rapid atrial pacing algorithms to terminate atrial re-entry.48
Sudden death
Small numbers of sudden deaths among patients with TGA mean that the usefulness of prophylactic cardioverter-defibrillator implantation cannot easily be systematically studied. Defibrillators are currently favored in patients who are deemed to be at a particularly increased risk (e.g. a history of syncope with ventricular arrhythmias on Holter monitoring) but this approach relies on clinical judgment.49 Although ventricular stimulation studies are used by many physicians to aid decision-making, the positive and negative predictive value of this test in patients who have undergone atrial-level repair is unknown. A defibrillator can be placed in the same way as a transvenous pacemaker, with the defibrillator lead in the anatomic left ventricle. Despite the posterior position of the defibrillator coil in the left ventricle in relation to the anterior right ventricle, high defibrillation thresholds are not usually encountered. Consideration should be given to the use of a defibrillator lead without a proximal SVC coil to reduce the risk of stenosis or occlusion of the superior baffle limb.
Systemic ventricular dysfunction
Medical management of right ventricular dysfunction has advanced little in the past 10 years. The small numbers of patients with this anatomy has made systematic evaluation difficult. A multicenter, double-blind, randomized, placebo-controlled, crossover clinical trial was used to evaluate losartan in patients with systemic right ventricles.50 Of 29 patients studied, 21 had undergone atrial-level repair for TGA. Despite abnormal baseline values, after a 15-week intervention period, the losartan and placebo-treated groups did not differ in terms of VO2max during exercise, right ventricular ejection fraction, or brain natriuretic peptide levels. The duration of therapy in this study was, however, short. A nonrandomized study in a small group of patients also failed to show a difference from baseline in exercise testing parameters between patients treated with enalapril for 1 year and patients receiving placebo.51 Right ventricular ejection fraction and other parameters improved slightly with medication in one small study,52 but the relevance of these results is unclear.
Although no high-quality data support the use of angiotensin-converting-enzyme inhibitors in patients with right ventricular dysfunction following atrial-level repair, many cardiologists feel that the risks associated with these agents are low and that use of these drugs or angiotensin-receptor blockers might be of benefit.
Small retrospective studies have suggested a beneficial effect of 
-blockers on functional class, exercise capacity, systemic right ventricular function and systemic atrioventicular valve regurgitation;53, 54 however, the small sample sizes (6 patients in one study, 31 in another), retrospective nature and limited methodologies of the studies make it difficult to conclude that -blockade is beneficial. From the standpoint of decreasing myocardial oxygen demand, the concept of -blockade certainly makes sense. Further work in this area is, however, clearly needed.
Originally thought to improve the systemic right ventricular function and prevent atrial arrhythmias, many patients with TGA have taken digoxin since childhood;19 however, few objective data support the use of this medication. We generally do not stop this medication, but we rarely initiate it in patients who have not previously taken it.
Conversion to arterial switch
If the systemic right ventricle is failing after an atrial-level repair, one might think that undoing the atrial baffle and performing an arterial switch operation in its place might be a good idea. The first step in such an approach is a surgically placed pulmonary artery band. This is necessary because the left ventricle rapidly becomes deconditioned when exposed to the low-resistance pulmonary circuit, losing its ability to generate systemic pressure. Conversion to an arterial switch repair to overcome this problem must, therefore, be approached by first surgically narrowing the pulmonary artery by banding to increase the pressure load of the left ventricle. After an interval of a few weeks to a few months, the atrial baffle can be taken down, the pulmonary artery band removed, and the arterial switch procedure performed. Unfortunately, this staged surgical approach has provided disappointing results.
The largest case series of conversion to arterial switch was reported by Poirier et al.55 In 35 patients, two-stage arterial switch was attempted following atrial-level repair for TGA. Among this cohort, 10 patients (28%) did not tolerate pulmonary artery banding: five patients died, four underwent heart transplantation, and one band remained in place at the time of reporting. Among the 25 patients who went on to have the baffle taken down and arterial switch performed, there were four early deaths, and three additional late deaths. In all, this strategy resulted in a survival rate of 51% (18/35) over a mean follow-up of 8.2 years (range 1–16 years). Further data analysis showed that age older than 12 years was a risk factor for left ventricular failure and death. Similarly sobering results were published by Mavroudis and Backer,56 showing that only 4 of 11 patients completed the switching protocol; the other 7 patients died or required heart transplantation.
While a gradual surgical tightening of the pulmonary artery band has been advocated as a way to improve outcomes,57 the two-stage conversion approach remains very high risk in adults, and for symptomatic patients must be considered in the context of continued medical therapy or transplantation. For asymptomatic patients, natural survival seems to favor keeping the current anatomy over an arterial switch strategy.
Heart transplantation
For patients with symptomatic heart failure, cardiac transplantation remains an alternative. Data from an international heart transplant registry show a half-life of 9.6 years overall for adults undergoing cardiac transplantation, but patients with congenital conditions had a relative mortality risk that was 2.5 times higher than that of the rest of the cohort.58
Cardiac resynchronization therapy
Biventricular pacing has been reported to improve clinical symptoms in a small cohort of patients with heart failure and TGA after atrial-level repair.59 The left ventricular pacing lead can be placed transvenously; whereas the systemic right ventricular lead needs to be placed epicardially because the coronary sinus still resides in the left atrioventricular groove in TGA and, therefore, does not provide access to the systemic right ventricle. This approach is worth considering in patients with symptomatic heart failure, especially if the native QRS is wide or the patient is primarily pacing the ventricle already. The small numbers of patients with symptomatic heart failure means that this area is not likely to be advanced by randomized studies.
Baffle problems
For systemic venous-baffle stenosis, transcatheter dilatation, stenting, or both is feasible.60 If the orifice shows acquired atresia, a stiff wire, radiofrequency perforation wire or a Brockenbrough needle can be used to perforate the atretic segment and a stent implanted to re-establish patency of the SVC baffle limb.60, 61 Pulmonary venous baffle obstruction can also be treated with transcatheter dilatation.62 For baffle leaks, transcatheter devices designed to close atrial septal defects have been deployed.63
Surgical baffle revision is now uncommon. Given the fading surgical experience with these types of repairs, and the high risk of reoperation (36% mortality in the Congenital Heart Surgeons Registry3), other approaches seem more favorable.
Pregnancy
Pregnancy has generally been well tolerated in patients with atrial-level repairs who are asymptomatic at baseline.64, 65, 66, 67, 68 Some data have shown worsening right ventricular dilation and tricuspid regurgitation that did not improve postpartum.68 Patients with the most-severe symptoms, who develop worsening systemic ventricular function and tricuspid regurgitation, can require hospitalization for medical management of heart failure symptoms in the last trimester. Worsening arrhythmias have been problematic in some pregnancies.64, 67 A small case series suggested the rate of preterm delivery was increased in women with atrial-level repair.67 The risk of heart disease in the offspring of these patients seems to be low.
Although most women who are in NYHA functional class I or II before pregnancy will tolerate gestation and childbirth, pregnancy can be associated with a worsening of their cardiac status and this possibility should be carefully considered. Our clinical practice is to recommend prophylactic pacemaker implantation before planned pregnancy, to decrease the double burden that both bradycardia and the increased circulating blood volume of pregnancy places on the systemic right ventricle. In addition, pacing can decrease the risk of atrial arrhythmias, as well as enable manual pace-termination of atrial flutter as an alternative to cardioversion or medical therapy during pregnancy. Angiotensin-converting-enzyme inhibitors and other potentially teratogenic medications should be stopped before conception.
Vaginal delivery remains the preferred mode of childbirth in asymptomatic women. In patients who become clinically compromised during pregnancy, caesarean delivery may be a more hemodynamically safe mode of childbirth.
Conclusions
Patients with TGA and atrial-level repairs represent an important group of adults with congenital heart disease. Most patients are asymptomatic but require ongoing, knowledgeable follow-up by specialized care-givers to optimize their longevity and quality of life.
Key points
- Patients who have undergone atrial-level repair for transposition of the great arteries comprise an important group of adults with congenital heart disease
- Although most adult patients with atrial-level repair continue to do well clinically, there remains a steady attrition, mainly owing to sudden arrhythmic death and systemic ventricular dysfunction
- Late morbidity includes sinus node dysfunction, atrial flutter, systemic ventricular dysfunction, systemic atrioventricular valve regurgitation, and stenosis of the superior vena caval baffle
- Interventional therapy is available for sinus node dysfunction, atrial flutter, baffle stenoses and other anatomic problems; a thorough understanding of the cardiac anatomy is required for successful application of these techniques
- Interval follow-up is required in all patients and systemic ventricular function should be followed
- At this time, data do not indicate that decline in ventricular function can be prevented by medical therapy
- Pregnancy and childbirth is possible for women with this anatomy albeit at some increased risk of worsening ventricular dysfunction and systemic atrioventricular valve regurgitation
Acknowledgments
Charles P Vega, University of California, Irvine, CA, is the author of and is solely responsible for the content of the learning objectives, questions and answers of the Medscape-accredited continuing medical education activity associated with this article.
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Competing interests
The authors declared no competing interests.
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Subject areas under which this article appears: Congenital disease | Intervention
