Definition and Morphology
Congenitally corrected transposition of the great arteries (CCTGA) was described in 1875 by von Rokitansky and is characterized by atrioventricular (AV) and ventriculo-arterial (VA) discordance. CCTGA may also be referred to as ventricular inversion or L-transposition of the great arteries. Visceroatrial situs may be solitus or inversus. Ventricles may be L-looped or D-looped. The aorta (Ao) is typically located anterior and leftward. In situs solitus, the ventricles are inverted, placing the morphologic right ventricle (RV) to the left. {S,L,L} and {I,D,D} denote the most common arrangements. CCTGA occurs in isolation or, more commonly, with associated anomalies that create up to 13 anatomic subtypes of complex CCTGA. The heart is usually left-sided (levocardia) or midline (mesocardia). Dextrocardia is noted in 20% of CCTGA patients. We use the term “corrected” because the double discordance maintains the physiologic direction of blood flow. Systemic venous blood returns to the right atrium, flows through the mitral valve (subpulmonary AV valve) into the subpulmonary left ventricle (LV) to be pumped through the pulmonary valve in the pulmonary artery (PA). Pulmonary venous blood returns to the left atrium, flows through the tricuspid valve (TV or systemic AV valve, SAVV) in the systemic right ventricle (SRV) to be pumped through the aortic valve in the Ao. Due to congenital redirection of blood flow, selected patients with CCTGA may go unrecognized in childhood and survive to an old age. However, the frequent occurrence of associated anomalies and the dependence on an SRV often lead to a markedly reduced life expectancy. Therefore for many patients, corrected transposition is an “uncorrected misnomer.” This chapter focuses on CCTGA with two functional ventricles. The management of CCTGA with a crisscrossed AV relationship and of single ventricle physiology with L-positioned great arteries is covered elsewhere.
Associated Anomalies
Ventricular Septal Defect
Ventricular septal defect (VSD) occurs in 70% to 88% of CCTGA patients. VSD locations are perimembranous (37%), conoventricular (38%), in the inlet (13%), or in the muscular septum (4%).
Pulmonary Stenosis
Pulmonary stenosis (PS) occurs in 50% to 70% of CCTGA patients ; it may be valvular (51%), subvalvular (42%), or there may be pulmonary atresia (6%). An aneurysm of the interventricular septum, fibrous tissue tags, a discrete ring, abnormal attachments from the mitral valve, or the position of the LV outflow tract and pulmonary valve between the mitral and TVs may all contribute to subpulmonary obstruction. PS is associated with a reduced long-term incidence of heart failure, SAVV regurgitation (SAVVR), and SRV dysfunction in adults with CCTGA.
Systemic Atrioventricular Valve (Tricuspid Valve)
In CCTGA, the morphologic TV acts as the SAVV; it is abnormal in 29% to 70% of patients. Ebstein-like anomaly of the left-sided TV differs from the right-sided form. They only have in common an extensive inferior displacement of the septal and posterior TV leaflets into the SRV cavity. The point of maximal displacement is the commissure between the septal and posterior leaflets. These leaflets may attach normally or be plastered to the ventricular wall. In the left-sided Ebstein anomaly, the AV sulcus circumference is not increased, and there is less thinning of the atrialized RV. The anterior leaflet is not sail-like but it is frequently cleft and may interfere with the SRV outflow; the ventricular cavity receiving the abnormal TV is small rather than dilated. When not displaying features of Ebstein anomaly, the abnormally formed TV has thickened leaflets and shortened chordae. A straddling TV, with chordae crossing through the VSD to attach in the contralateral ventricle, may preclude biventricular repair. The TV may also override the interventricular septum.
Coronary Arteries
Coronary artery anatomy is important for planning surgical repair. Coronary arteries in CCTGA usually originate from the posterior, or facing, aortic sinuses and they are concordant with the ventricle that they supply. The left coronary artery originates from the right sinus, and the right coronary artery originates from the left sinus. The SRV receives its blood supply from the morphologic right coronary artery. There may be a single coronary artery that originates from the right sinus of Valsalva and trifurcates into a circumflex artery, a left descending artery, and a third coronary artery following the usual course of the right coronary artery.
Conduction System
The sinus node is in the normal position. The AV node is situated anteriorly in the right atrium at the lateral junction of the pulmonary and mitral valves. In the presence of dual AV nodes, only the anterior AV node connects with the His bundle. The posterior AV node, in the position of the AV node of a normal heart, is hypoplastic and does not connect with the ventricles, except in situs inversus where it gives rise to the conduction system. An anterior bundle descends into the morphologic LV and encircles the antero-lateral quadrant of the pulmonary valve. In the presence of a VSD, the conducting tissue lies near the anterior quadrant of the defect. The bundle reaches the anterior portion of the ventricular septum, where it bifurcates. Bundle branches are inverted. A thin sheet of left bundle branch fibers reaches the middle portion of the left side of the interventricular septum and then fans out deep in the LV. The right bundle branch enters the RV and passes beneath the conal papillary muscle before fanning out in the anterior trabeculae of the RV.
Other Associated Lesions
An atrial septal defect (55%), patent ductus arteriosus (33%), left superior vena cava to the coronary sinus (17%), double-outlet RV (18%), complete AV canal (6%), abdominal heterotaxy (8%), coarctation of the Ao (5%), and mitral (subpulmonary AV valve) anomalies (5%) such as a cleft, may also occur in association with CCTGA.
Genetics and Epidemiology
CCTGA is a rare disease, accounting for less than 1% of congenital heart diseases. The prevalence of transposition of the great arteries, both complete and congenitally corrected, is estimated at 0.04 cases per 1000 adults in a population study. The genetics and inheritance of CCTGA remain incompletely understood. Patients rarely have chromosomal or extracardiac anomalies. An association between heterotaxy and both transposition of the great arteries and CCTGA is observed.
Presentation and Management in Childhood
CCTGA is compatible with normal prenatal growth and development. Closure of the ductus arteriosus is well tolerated by the term neonate. The combination of complete heart block with a patent ductus arteriosus may put the neonate at risk for cyanosis because the long diastolic time favors steal from the systemic circulation. In childhood, CCTGA presents with cyanosis (47% to 54%), arrhythmia (32%), or heart failure (25% to 39%); only 5% of children with known CCTGA are asymptomatic. Heart failure is secondary to pulmonary overcirculation and hypertension in the case of a VSD or to pulmonary congestion in the case of severe SAVVR. It may be treated initially with diuretics, digoxin, and vasodilators. The combination of LV outflow tract obstruction and a VSD may lead to significant cyanosis.
Symptoms, the nature of associated anomalies, and their extent dictate the need and timing for intervention in the pediatric population. Asymptomatic infants with a VSD and PS may undergo repair at 6 to 12 months, when the retrosternal space will accommodate a large RV- or LV-to-PA conduit, without distortion or coronary artery compression. If the child becomes cyanosed, a modified Blalock-Taussig shunt can be inserted. Symptomatic children undergo conventional (functional) or anatomical (double-switch) repairs. No significant differences in outcomes could be found between these types of repair, and therefore both strategies are used. Conventional repairs consist of VSD closure, relief of pulmonary outflow obstruction, LV-PA conduit placement and TV repair or replacement, alone or in combination. This strategy leaves the TV and the RV in systemic positions. Several observations question the capacity of the SRV and TV to provide lifelong support to the systemic circulation and favor anatomic repairs that replace the TV and morphologic RV in the subpulmonary position. Anatomic repairs are preferred for children younger than 15 years old with a failed conventional repair and significant tricuspid valve regurgitation (TR), severe SRV dysfunction, or both.
Conventional Repairs in Children
Conventional (functional) repairs are performed with notable operative mortality ( Table 53.1 ), which appears higher than for anatomic repair, although patients may be less pre-selected. Long-term survival may be low (48% to 90%, see Table 53.1 ) depending on the surgical era. Postoperative heart block requiring pacing occurs in 4% to 32% of patients.
| Author | Year | N | Age (yrs) | FU (yrs) | Mortality | Survival | Heart block | ||
|---|---|---|---|---|---|---|---|---|---|
| Op | At end FU | 10 yrs | 20 yrs | ||||||
| Conventional Repair | |||||||||
| Hirose | 2015 | 23 | — | 11-21 | 13% | — | 95% | 90% | 4% |
| Hsu | 2015 | 15 | 17 | 10 | 13% | — | — | 80% ∗ | 7% |
| Shin’oka | 2007 | 67 | 12-13 | 10 | — | — | — | 62-78% † | — |
| Hraska | 2005 | 113 | — | 4 | — | — | 68% | 28% | |
| Yeh | 1999 | 118 | 0-65 | 8 | 5% | 29% | 75% | 48% | 28% |
| Termignon | 1996 | 52 | 26-33 | 5-8 | 15% | 55-71% | — | 27% | |
| Szufladowicz | 1996 | 90 | 0.5-30 | — | 14% | — | — | 70% | 20% |
| Sano | 1995 | 28 | — | — | 4% | — | 83% | — | 9% |
| McGrath | 1985 | 99 | — | — | 14% | — | 68% | — | 26% |
| Metcalfe | 1983 | 19 | 1.1-47 | 3-8 | 37% | 21% | — | — | 32% |
| Anatomic Repair | |||||||||
| Hsu | 2015 | 18 | 8.4 | 5 | 22% | — | 53% | — | 6% |
| Bautista-Hernandez | 2014 | 106 | 0.2-43 | 5 | 6% | 3% | — | — | 38% |
| Hiramatsu | 2012 | 90 | 4-7 | 11-13 | — | — | — | 76-83% | 9% |
| Murtuza | 2011 | 113 | 0.07-40 | — | 4% | — | 77-84% | — | 16% |
| Ly | 2009 | 20 | 2.2 | 5 | — | — | 100% | — | 20% |
| Shin’oka | 2007 | 84 | 5-7 | 10 | — | — | 75-80% ‡ | — | |
| Langley | 2003 | 54 | 0.1-40 | 4 | 6% | — | 90% | — | 14% |
| Ilbawi | 2002 | 12 | 0.75 | 8 | 9% | 9% | — | — | 9% |
| Yeh | 1997 | 10 | 0-65 | 2 | 11% | 11% | — | — | 50% |
| Imai | 1994 | 18 | 1.3-12 | 2 | 11% | 11% | — | — | 0% |
† 27-37 years survival depending on the cohort;
‡ 15-16 years survival depending on the cohort; empty fields denotes unavailable data.
In AV discordance, surgical VSD closure is performed by placing the suture line on the morphologically right side of the septum without opening the systemic ventricle to reduce the incidence of AV block. PA banding is performed in selected cases as an interim step to allow for growth prior to VSD closure.
Management of TR, when the TV acts as the SAVV, is complex. In CCTGA, the overall prevalence of SAVVR increases as children age, going from 36% to 64% during follow-up in one series. Worsening SAVVR is associated with an abnormal TV, VSD closure, aortopulmonary shunts, and complete AV block. Patients with moderate SAVVR after VSD closure and patients who require TV intervention fare poorly. TV competence should therefore be maintained as part of the early management of CCTGA patients, especially while SRV ejection fraction remains above 40% to 44%, which is more likely early in life. Patients with a VSD and PS have the best survival, possibly because PS induces septal shift toward the SRV and reduces TR, as observed after PA banding. In CCTGA without PS, early PA banding may be advocated to reduce TR and in preparation for anatomic repair. Acar et al. urge surgeons to minimize the use of aortopulmonary shunts that increase flow through the TV as well as repairs that decrease LV pressure, modify septal geometry, and increase TR (VSD closure, relief of PS). TV repair produces disappointing results when it is in the SAVV position. TV replacement in a growing child generates many hurdles, including eventual patient-prosthesis mismatch and the need for long-term anticoagulation for a mechanical prosthesis.
Anatomic Repair
The concept of this complex procedure is to restore the LV as the systemic pumping chamber and to remove the abnormal TV from the SAVV position. It combines an atrial switch operation (Mustard or Senning operation) with an arterial switch operation. The VSD is closed with a patch. Candidates for a double-switch operation have no right or left outflow tract obstructions, balanced ventricular and AV valve sizes, a septatable heart, no major AV valve straddling, translocatable coronary arteries, LV/RV pressure ratio greater than 0.7, competent mitral valve, and good LV function. In the presence of pulmonary outflow obstruction or pulmonary valve stenosis, the atrial switch operation is performed in combination with a Rastelli operation. Provided that the VSD is adequately sized and positioned, the LV outflow is tunneled to the Ao via the VSD and a valved conduit is placed between the RV and PA. If PS did not maintain the LV pressure at the systemic level, LV retraining is necessary by placing a PA band. The goal is to raise the LV pressure to 75% to 80% of systemic arterial pressure for 6 to 12 months, aiming for an LV volume-to-mass ratio greater than 1.5. Successful LV retraining is uncertain after 15 years of age, precluding the use of this strategy in adults. Aortic root translocation with atrial switch has also been described to achieve anatomic repair of CCTGA. Complications after anatomic repair include complete heart block, systemic venous baffle obstruction, pulmonary venous baffle obstruction, residual VSD, aortic regurgitation (double switch), or RV-PA conduit obstruction (Rastelli).
Anatomical repair for CCTGA has almost exclusively been performed in infants and children, with good operative outcome (see Table 53.1 ). Postoperative survival at 10 years appears better than with conventional repairs, but longer follow-up data have yet to become available (see Table 53.1 ). Heart block requiring pacing does not appear to be substantially less common than after conventional repairs (see Table 53.1 ). LV dysfunction occurred in 12% of patients at 5 years follow-up in one series. In cases in which anatomic repair is not possible, performing a Fontan operation may lead to better survival than reverting to a conventional repair.
Presentation and Management in Adulthood
Adults with CCTGA may be unoperated, or even undiagnosed, or may have undergone prior conventional repair (15% to 70%, depending on the cohort, Table 53.2 ). The majority of adult patients with CCTGA have an SRV. Young adults having undergone anatomic repair will eventually enter adult congenital heart disease clinics. Symptomatic patients most often have SAVVR and heart failure (see Table 53.2 ).
