Ventricular Septal Defect

This is the most common abnormality to coexist with TGA, occurring in 40% to 45% of cases. The size and position of such defects within the ventricular septum are variable, but the most common types are perimembranous defects and muscular defects, occurring with approximately equal frequency. Associated malalignment of the outlet septum is common in these types of defect, with some degree of malalignment in up to 75% of cases. Less common types of defect are atrioventricular septal defects and doubly committed subarterial defects, each making up approximately 5% of the total. Small defects, especially in the muscular septum, are likely to close spontaneously, but larger defects will generally need surgical management.

Left Ventricular Outflow Tract Obstruction

This abnormality is second in frequency to VSDs, occurring to some degree in up to 25% of patients. It is more likely to occur in patients who also have a VSD. The anatomy of the obstruction is somewhat variable but most commonly involves either a subvalvar fibrous membrane or a combination of valvar and muscular subvalvar stenosis. Less common types of obstruction are due to abnormal chordal attachments of the mitral valve into the ventricular septum below the pulmonary valve or aneurysm formation of the membranous septum.

In patients who have undergone atrial baffle repair of TGA, there is commonly a gradient across the LVOT due either to bulging of the ventricular septum into the outflow tract or to systolic anterior motion of the mitral valve. In most cases, the gradient is relatively mild, although in a minority it may be more severe, leading to the development of systemic pressures within the LV. Such pressure loading of the LV may be potentially beneficial in that it may render the patient suitable for a late arterial switch conversion (see later).

Coarctation of the Aorta

Aortic coarctation is seen in approximately 5% of patients with TGA. It may be a discrete shelflike lesion or may be associated with hypoplasia of the distal aortic arch. Coarctation is more common in patients with malalignment-type VSDs and may be associated with some degree of subaortic narrowing in this situation.

Mustard and Senning Operations

The first definitive operations for TGA were described by Senning in 1959 and Mustard in 1964. Both of these procedures “correct” the physiological abnormality of the transposed great arteries by forming a baffle within the atria to “switch” the flow of blood at inflow level. This results in a reversion to the normal flow of blood with the heart and lungs being in series; however, the LV remains the subpulmonary ventricle and the RV the systemic ventricle.

The main difference between the two procedures is that in the Senning operation the baffle is created from right atrial wall and atrial septal tissue without the use of extrinsic materials; however, the Mustard operation involves resection of the atrial septum and the creation of a baffle from pericardium or synthetic material ( Fig. 51.3 ). These operations were performed at varying stages of life but usually between 1 month and 1 year of age. In experienced hands the early mortality rate associated with these procedures is low, with a surgical mortality rate generally between 1% and 10% ( Box 51.1 ).

The Mustard operation for transposition of the great arteries. A, Surgeon’s view of the right atrium. B , The right atrium is opened, and the atrial septum is excised. C, The pericardial baffle is initially sutured around the left pulmonary veins. D, The baffle is completed. E, The right atrium is closed. Ao , Aorta; CS , coronary sinus; MV , mitral valve; SA , sinoatrial; SVC , superior vena cava; TV , tricuspid valve.

(Modified from Kirklin JW, Barrett-Boyes BG. Complete transposition of the great arteries. In: Kirklin JW, Barrett-Boyes BG, eds. Cardiac Surgery . 2nd ed. New York, NY: Churchill Livingstone, White Plains; 1993:1383-1467).

Arterial Switch Operation

The successful anatomic correction of TGA was first described in 1975 by Jatene et al. This procedure involves transection of the aorta and pulmonary artery at a level above the valve sinuses. The coronary arteries are detached from the aorta with a surrounding “button” of aortic wall and sutured into place in the neoaorta. Finally, the pulmonary trunk is moved forward into its new position anterior to the aorta, and the switched great arteries are sutured into place ( Fig. 51.4 ). The arterial switch is a technically challenging operation, but has the great advantage over the Mustard or Senning procedure in that the LV becomes the systemic ventricle.

The Rastelli operation for transposition of the great arteries with ventricular septal defect (VSD) and pulmonary outflow obstruction. A , Surgeon’s view of the right ventricle. B, The right ventricle is opened and the VSD enlarged if necessary. C, The entrance to the pulmonary artery is closed. D and E, A patch is sewn into place to create a tunnel from the left ventricle across the VSD to the aortic valve. F, A valved conduit is prepared and sutured to the pulmonary artery. G, The proximal end of the conduit is sutured to the right ventriculotomy. Ao, Aorta; MV, mitral valve; SVC, superior vena cava.

(Modified from Kirklin JW, Barrett-Boyes BG. Complete transposition of the great arteries. In: Kirklin JW, Barrett-Boyes BG, eds. Cardiac Surgery . 2nd ed. New York, NY: Churchill Livingstone, White Plains; 1993:1383-1467).

The procedure is usually performed within the first 2 weeks of life and should be undertaken at the latest by 4 to 6 weeks of life. After this time the patient with TGA and intact ventricular septum will have suffered significant regression of left ventricular muscle mass due to its functioning at low pressure in the pulmonary circuit. This thinning of the left ventricular myocardium increases the potential for left ventricular failure after the arterial switch procedure and increases surgical risk.

Rastelli Operation

The most frequently used surgical option for patients with the combination of TGA, pulmonary outflow tract obstruction, and VSD is the Rastelli operation ( Fig. 51.5 ), which was originally described in 1969. Concern about the long-term outcome of Rastelli patients has led to the development of the related Reparation a l’etage ventriculaire (REV) procedure, Metras modification, and Nikaidoh procedure.

The arterial switch operation for transposition of the great arteries (TGA). A, Surgeon’s view of the heart. Sinus 1, left-facing sinus; sinus 2, right-facing sinus. B, Dashed lines indicate the sites of transection of the aorta and main pulmonary artery. C, The aorta is transected. D, The pulmonary trunk is transected. E, A button of aorta is excised around the ostium of the left main coronary artery. F, An incision is made in the left-facing sinus of the neoaorta, into which the left coronary button will be sutured. G, The right coronary artery button is excised and sutured on to the neoaorta in similar fashion. H, The distal ascending aorta is brought under the pulmonary bifurcation (the Lecompte maneuver) and is anastomosed to the proximal portion. Pericardial patches are sewn into the neopulmonary trunk to fill the defects left by the coronary buttons. I, The proximal and distal portions of the neopulmonary trunk are anastomosed. Ao , Aorta; IVC , inferior vena cava; LAD , left anterior descending artery; LPA , left pulmonary artery; PA , pulmonary artery; RCA , right coronary artery; RV , right ventricle; SVC , superior vena cava.

(Modified from Kirklin JW, Barrett-Boyes BG. Complete transposition of the great arteries. In: Kirklin JW, Barrett-Boyes BG, eds. Cardiac Surgery . 2nd ed. New York, NY: Churchill Livingstone, White Plains; 1993:1383-1467).

The Rastelli operation uses the VSD as part of the LVOT and involves placement of a baffle within the RV, directing blood from the VSD to the aorta. The pulmonary valve or subpulmonary region is oversewn, and a conduit is inserted between the RV and the pulmonary artery. Suitability for the Rastelli operation is dependent on appropriate VSD anatomy: the defect should be large and subaortic in position. Surgical enlargement of the VSD may be undertaken but carries with it a risk of inducing complete heart block and has been shown to be associated with less good long-term outcomes.

The main advantage of this operation is that the LV becomes the systemic ventricle. The most important limitation is that the patient is committed to further operations because the pulmonary conduit is likely to need replacing several times during the patient’s life.

There is continuing debate regarding the most appropriate timing of the Rastelli operation. Some believe that the procedure should be performed during early infancy, citing the advantages of early physiological correction, less time spent with systemic hypoxemia, and avoidance of a left-to-right shunt from palliative procedures. Others believe that a palliative procedure is the most appropriate first intervention, usually a modified Blalock-Taussig shunt. The reasons cited would be the higher risks associated with early repair and that a smaller conduit will require earlier reoperation.

Survival and Functional Status

Surgical mortality rates after the Mustard and Senning operations were low in most centers that performed large numbers of these operations. A review of the literature concerning operations performed between 1971 and 1979 showed a mean hospital mortality rate of 4.8%. A large single-center review showed that the surgical mortality rate fell significantly in the second half of the series, with a mortality rate of 10.4% between 1963 and 1973 and 0.9% between 1974 and 1985. Early mortality after repair of patients with associated lesions is significantly higher. In the literature review quoted above, the average mortality for patients with TGA and VSD was 23%, and although more recent results show improved outcome for this population, the surgical risk is clearly higher.

The Mustard and Senning procedures were superseded by the arterial switch operation in the mid to late 1980s in most surgical centers, and the population of patients who have undergone these procedures is therefore essentially complete. Unfortunately these patients have several issues leading to late morbidity and mortality, especially as the population ages.

Late survival data after atrial baffle repair show a small but ongoing attrition rate, with the most frequent causes of death being sudden death and systemic right ventricular failure. In one large single-center series, the 5-year survival rate was 89% and the 20-year survival rate 76%. Another large series showed a 90% 10-year and an 80% 20-year survival rate. A large study showed a 30-year survival rate of 60%. Some studies have suggested somewhat better long-term survival in Senning patients compared with Mustard patients.

Survival rates after repair of TGA and VSD are again less good, with 5-year survival rates of 60% to 70%. Risk of late death after atrial baffle repairs is 2.7 times greater in patients with a VSD, relative to those with an intact ventricular septum.

Functional status is reasonably good in this population, with around 60% to 80% of patients in many series being in functional class I and the majority of the remainder being in class II. Nevertheless, overall functional class does appear to be declining with increasing length of follow-up. Formal testing demonstrates that the exercise capacity of the atrial baffle population as a whole is reduced relative to the normal population, with the most significant cause of limitation appearing to be chronotropic incompetence. The stroke volume response to exercise is also reduced secondary to a failure to augment ventricular filling rates during tachycardia, presumably due to the abnormal characteristics of the atrial baffles. Peak oxygen uptake is also reduced in this population, being 65% predicted in one large study, with peak oxygen uptake and minute ventilation-carbon dioxide production relationship (VE/VCO ₂ slope) predicting event-free survival.

Arrhythmias and Sudden Cardiac Death

Patients who have undergone the Mustard or Senning procedure are at risk of both bradyarrhythmias and tachyarrhythmias. The most common tachyarrhythmia is an incisional atrial reentry tachycardia, sometimes described as atypical atrial flutter. The most common bradyarrhythmia is sinus node dysfunction leading to sinus bradycardia with a junctional escape rhythm.

Ventricular Function

The main concern regarding the long-term outlook for patients with atrial baffle repairs of TGA has been the function of the systemic RV. Although it is clear that the RV can tolerate functioning at systemic pressures in the short to medium term without difficulty, it may potentially fail when required to do this in the long term. Studies using magnetic resonance imaging (MRI) and echocardiography have consistently shown significant rates of right ventricular dysfunction in this population. A study from the Netherlands reviewing 91 patients after the Mustard operation showed that all patients had good function or mild dysfunction 14 years after repair. However, when the group was restudied at a median follow-up of 25 years, 61% had moderate or severe dysfunction. At most recent follow-up, a mean of 35 years since surgery, only one of 47 patients had normal right ventricular function. Therefore our concern is that patients with mild right ventricular dysfunction in the third decade of life may progress to more severe dysfunction over the decades to come. We have observed several patients in our own clinic who have had quite rapid progression of right ventricular systolic dysfunction to the stage in which this becomes severe. As yet there are no clear risk factors that predict the development of severe right ventricular dysfunction in this population, although research in our group suggests that there may be a relationship with the degree of right ventricular hypertrophy: those with the most severe hypertrophy having less good ventricular function. This research potentially fits in with the finding that the great majority of atrial baffle patients have right ventricular myocardial perfusion abnormalities. It is possible that the greatly increased coronary demand of the systemic RV outstrips the available coronary supply from a morphologic right coronary artery system. Several small studies assessing the use of ACE inhibitors or angiotensin receptor blockers have not demonstrated any significant benefit.

Tricuspid Valve Function

Mild-to-moderate tricuspid regurgitation is relatively common in patients after atrial baffle repair of TGA. The reversal of the right and left ventricular pressure relationship results in altered geometry of the ventricular septum. Therefore the tricuspid valve takes on a more rounded shape, which in combination with the displaced septal chordal attachments of the valve results in an increased tendency to tricuspid regurgitation. Severe tricuspid regurgitation in patients without associated lesions is unusual in most series and when present may reflect severe ventricular dysfunction and dilatation. In patients with associated VSD the incidence of important tricuspid regurgitation is higher (approximately 5% to 10%) partly due to damage to the valve and its support apparatus during operation. In this case, repair or replacement of the valve may be justified to reduce volume loading and prevent progressive deterioration of right ventricular function. However, tricuspid valve repair in the context of moderate or severe RV dysfunction is unlikely to be successful, and valve replacement is unlikely to be beneficial and may carry significant risk.

Baffle Obstruction and Baffle Leaks

Baffle obstruction is an infrequent but important late complication after the Mustard and Senning operations. Superior limb systemic venous baffle obstruction occurs with a frequency of approximately 5% to 10% in Mustard patients, whereas inferior limb obstruction occurs infrequently, with an incidence of only 1% to 2%. Mild obstruction can be managed expectantly, although more severe stenosis may require surgical or catheter intervention. Pulmonary venous baffle obstruction is also infrequent, occurring with a frequency of approximately 2%. Severe obstruction of the pulmonary venous channel will lead to the development of pulmonary hypertension and therefore pressure loading of the morphologic LV, which in turn may render the patient suitable for consideration of late arterial switch conversion.

Baffle leaks are more common than obstruction, the most common site being at the suture line of the superior limb of the systemic venous baffle. Baffle leaks have been shown to be present in up to 25% of patients, although most are not hemodynamically significant. Shunting may be either left to right or right to left. In patients with a large left-to-right shunt, the consequent volume loading of the systemic RV may necessitate reintervention to close the defect. In patients with important right-to-left shunts, systemic arterial desaturation will develop, likewise necessitating closure. However, these large shunts are rare, and only approximately 1% to 2% of atrial baffle patients will require reintervention for baffle leaks.

Pulmonary Hypertension

The late development of pulmonary vascular disease is a recognized complication after atrial baffle procedures, occurring with a frequency of approximately 7%. This complication is more common after late repair and in patients with an associated VSD.

Survival and Functional Status

Operative survival after the arterial switch in the current era is very good, with a surgical mortality rate of between 1% and 5% for patients without associated lesions. The operative mortality rate is higher in patients with an associated VSD but is still less than 5% in some series. Functional status is normal in the great majority of patients, and aerobic exercise capacity has been shown to be normal or low-normal relative to age- and sex-predicted values.

Mid- to long-term follow-up studies for the arterial switch operation are reassuring at this relatively early stage in the history of this procedure. A review of more than 1000 survivors showed an overall survival rate of 88% at both 10 and 15 years, with no deaths later than 5 years after operation. The results are somewhat less good in patients with associated lesions, with a survival rate of 80% at both 10 and 15 years, although the difference largely represents differing operative risk.

Data on late morbidity for the arterial switch are accruing, with many centers now able to examine outcomes for patients who are completing their third decade. Cardiac residua and sequelae have been reported in 25% to 40% of patients, including aortic root dilation, neoaortic regurgitation, right ventricular outflow tract obstruction, coronary abnormalities, and arrhythmia. Late residua are more common in those who required cardiac reintervention in childhood.

Arrhythmias and Sudden Cardiac Death

Sinus rhythm with normal conduction is maintained at medium- to long-term follow-up in 95% to 98% of arterial switch patients. There is a low incidence, less than 2%, of complete heart block, usually in patients who had an associated VSD. In one study the incidence of supraventricular tachycardia at medium-term follow-up was 4%, the majority occurring more than 1 year after the surgery. The incidence of late sustained ventricular arrhythmias was less than 0.5%. Sudden death is unusual in most series and is usually related to myocardial infarction secondary to coronary artery obstruction.

Ventricular Function

Good left ventricular function is the norm after the arterial switch operation, with more than 95% of patients having normal left ventricular systolic function at medium- to long-term follow-up. Severe ventricular dysfunction is an occasional complication in a small proportion of patients and is often associated with coronary artery abnormalities. Left ventricular dysfunction is a recognized cause of death in less than 1% of patients.

Pulmonary Artery Stenosis

Reintervention is required in at least 10% of patients after the arterial switch operation and in many cases is due to supravalvar main pulmonary artery stenosis or branch pulmonary artery stenosis. This occurs in at least 5%—and in as many as 25% of patients in some series—although recent results appear better. One large multicenter study showed freedom from pulmonary artery stenosis of 95%, 90%, and 86% at 1, 5, and 10 years, respectively. Surgical or catheter intervention to address pulmonary arterial stenosis is required in a significant minority of arterial switch patients. Small numbers of patients to date have required neopulmonic valve replacement as a late consequence of attention to relieve right outflow tract obstruction.

Neoaortic Valve Regurgitation

There appears to be an ongoing risk of the development of important aortic regurgitation, although only a small proportion has needed intervention at current stages of follow-up. In one large study the incidence of all grades of aortic regurgitation was 16% at a median follow-up of 4.9 years; however, only 3.8% had regurgitation of grade 2 or more. Freedom from reoperation for aortic regurgitation was 99.1%, 97.6%, and 96.2% at 5, 10, and 15 years, respectively. Risk factors for the development of important neoaortic valve regurgitation include size discrepancy between the great arteries, bicuspid pulmonary valve, LVOT obstruction, follow-up duration, and aortic root dilation.

Some degree of aortic root dilatation is almost universal in this population, and several studies have shown serial increases in aortic root Z scores with serial follow-up. Early data suggested that aortic dilatation may stabilize in adult life, but follow-up is too short at this stage to be certain of the natural history of this complication in adulthood. To date we have not seen complications, such as aortic dissection or rupture, but patients with severe aortic dilatation clearly need careful follow-up.

Coronary Arterial and Vascular Complications

In a large study of 1198 hospital survivors of the arterial switch 7.2% had coronary events, defined as death from myocardial ischemia/infarction, sudden death, nonfatal infarction or reoperation for coronary stenosis. The great majority of these events occurred in the first 3 months after the surgery. In a subset of 324 who underwent coronary angiography, 6.8% had significant lesions, 13 with coronary occlusions, and 9 with stenosis. A further 4% had minor coronary stenosis. Several other series have also reported coronary abnormalities and late deaths due to coronary events.

Because of the denervation of the heart at the time of the arterial switch operation, the symptoms of myocardial ischemia may be atypical, without classic angina, and it is therefore important to remain vigilant for the possibility of this complication.

Abnormalities of vascular function, including decreased arterial distensibility and increased pulse wave velocity have been demonstrated in late follow-up. Considered with the known risk of neoaortic root pathology and potential for increased late coronary vulnerability, these findings are now highlighting the potential need for proactive management of risk factors, including weight, physical activity, and smoking in this population.

Neurologic Outcomes

Follow-up studies have demonstrated increased neurodevelopmental risk in the arterial switch population. Although most scores on neuropsychological testing fall into the average range, studies have demonstrated substantial proportions below the expected mean. Magnetic resonance brain imaging studies in adolescents have demonstrated abnormalities in approximately one-third of adolescents. Preoperative acidosis, hypoxia, and perioperative seizures have been shown to be associated with later neurologic concerns.

Survival and Functional Status

Operative survival after the Rastelli operation was poor early in the surgical experience, with mortality rates of up to 30%; however, this has improved substantially such that more recent series report an operative mortality rate of 5% or less. There is a significant incidence of late mortality after Rastelli repair, with a large single center series reporting a survival rate of 82% at 5 years, 80% at 10 years, 68% at 15 years, and 52% at 20 years. The most common causes of late death or transplantation were left ventricular failure and sudden death. In a more recent European multicenter report including related operations, results were somewhat better in terms of short-medium term survival, with survival rates of 88% at 5 and 10 years, 85% at 15 years, and 58% at 20 years. A large single-center series suggests that long-term outcomes may be better after the REV procedure.

Functional status is often good in these patients, although the presence of conduit stenosis or important ventricular dysfunction may be limiting factors. Exercise capacity in the Rastelli population overall is reduced compared with that in the normal population.

Arrhythmias and Sudden Cardiac Death

There is a significant incidence of sudden death after the Rastelli operation, which is considered likely to be arrhythmic in nature. In one large series there was a high incidence of documented late arrhythmias, with approximately equal rates of ventricular and supraventricular tachycardia. There is also a risk of early or late development of heart block in these patients. The occurrence of ventricular tachycardia in particular may be associated with conduit obstruction and right ventricular hypertension and should direct the physician towards a detailed hemodynamic assessment of the patient.

Ventricular Function

Left ventricular dysfunction is present in approximately 25% of Rastelli patients at late follow-up and is a cause of late death in a significant minority. Right ventricular dysfunction is also common, often secondary to the abnormal pressure and/or volume load related to conduit dysfunction.

Conduit Stenosis and Outflow Tract Obstruction

Development of stenosis of the RV-pulmonary artery conduit after childhood Rastelli procedure is inevitable. Most patients who undergo the Rastelli procedure will require multiple conduit replacements during a normal lifespan because the longevity of currently used bioprosthetic conduits is between 10 and 20 years. The use of percutaneous implantable valves in these situations is now widespread, but concerns exist about the increased risk of endocarditis associated with these valves. Vigilance for the development of conduit stenosis or regurgitation is important throughout life in this population. LVOT obstruction is less common but equally important and should be detected by careful clinical and echocardiographic evaluation.