Congenitally corrected transposition of the great arteries (CCTGA) is an uncommon cardiac anomaly. It is characterized by atrioventricular (AV) and ventriculoarterial (VA) discordance (Fig. 10.1). The discordance of both the AV and VA connections results in a situation where the systemic and pulmonary venous returns are appropriately directed to the pulmonary artery and aorta. However, the arrangement of the morphologic ventricles “between” the venous and arterial segments is the opposite of normal. The systemic venous return connects with the right atrium (RA) normally. The RA is then connected to the morphologic left ventricle (LV) via a mitral valve that is in turn connected to the pulmonary artery (PA). There is no subpulmonary infundibulum because this is a morphologic LV and therefore there is mitral valve–pulmonary valve fibrous continuity. The pulmonary veins connect to the left atrium (LA). The LA is then connected to a morphologic right ventricle (RV) via a tricuspid valve. The RV (systemic ventricle) is connected to the aorta. In CCTGA, the aorta is usually positioned anterior and leftward of the pulmonary artery with a well-developed subaortic infundibulum resulting in discontinuity between the tricuspid and aortic valves.
CCTGA is often referred to as “l” (levo)-transposition of the great arteries. This “l” refers to the leftward embryologic looping of the ventricles and not the spatial relationship of the great arteries. It is a confusing term given that many other complex conditions, including forms of single ventricle, can have l-transposed (anterior and leftward) great arteries. Simply referring to CCTGA as “corrected transposition” is also inadequate since patients with complete or d (dextro)-TGA may have been “surgically corrected.” For these reasons, the authors prefer the term “congenitally corrected transposition of the great arteries (CCTGA)” to describe patients with AV and VA discordance.
Echocardiography is the imaging modality that provides the most robust diagnostic assessment of CCTGA. The unusual relationship between the two ventricles, ventricular septum, and the great arteries results in several unique echocardiographic features. Similar to other forms of transposition of the great arteries, the initial (unbranched) segments of the great arteries run parallel to each other (Fig. 10.2). In addition, unlike the normal heart, the ventricles assume more of a side-by-side relationship, and as result, the ventricular septum is oriented in a straight anterior–posterior plane (Fig. 10.3). In some cases, the ventricles are arranged in a superior-inferior manner with the morphologic RV being superior. The diagnosis of CCTGA is based on demonstrating discordance of both the AV and VA connections [RA → LV → PA, and LA → RV → aorta]. The spatial relationship of the great arteries supports the diagnosis of CCTGA; however, it should not be considered the sole diagnostic criterion.
Figure 10.1. Pathology specimen. A: Normal relationship of great arteries to the ventricles (ventriculoatrial [VA] concordance) and normally related atrioventricular (AV) relationships (AV concordance). B: Congenitally corrected transposition of the great arteries with AV discordance and VA discordance. Aorta is anterior and leftward to main pulmonary artery. (From the Dr. William Edwards collection, Mayo Clinic.)
Figure 10.2. Subcostal imaging with transducer angulated anterior to demonstrate parallel relationship of the great arteries.
The subcostal and apical four-chamber imaging planes are extremely useful in the examination of patients with CCTGA. The subcostal plane is used to define the atrial and visceral situs and the cardiac position. Twenty-five percent of patients with CCTGA have dextrocardia or mesocardia (Fig. 10.4). The subcostal views allow excellent imaging of the great arteries and their relationships to the ventricular chambers. From the subcostal coronal imaging plane, the parallel arrangement of the great arteries can be easily identified (see Fig. 10.2). In addition, the unique relationship of the LV outflow tract and the PA can be seen with pulmonary outflow tract deeply wedged between the right and left AV valves (Fig. 10.5). Most importantly, in this imaging plane, the relationship of the atria, ventricles, and the great arteries can be defined. As described in previous chapters in this textbook, a morphologic RV can be defined by the presence of several unique anatomic features:
1.apical position of the tricuspid valve septal leaflet hinge point (relative to the mitral valve anterior leaflet septal hinge point),
2.a “tricuspid” trileaflet AV valve with chordal attachments to the ventricular septum,
3.a moderator band,
4.an irregular (trabeculated) mural endocardial surface,
5.a pyramidal (instead of elliptical) shape to the ventricular cavity (see Fig. 10.3).
In the most common form of CCTGA (Fig. 10.6), the pulmonary veins will connect to the left-sided LA. The LA in turn connects to a morphologic RV via a tricuspid valve. The RV then connects to a great artery that arches and gives rise to coronary arteries, and is by definition the aorta. On the other side of the heart, the systemic veins connect to a right-sided RA, which then connects to a morphologic LV. The LV connects to a great artery that bifurcates into two branches, and is by definition the pulmonary artery. In the young patient, these connections and relationships can be observed from the subcostal transducer position.
Similar to the subcostal coronal imaging plane, the apical four-chamber plane is extremely useful in the setting of CCTGA. In fact, the key anatomic feature of AV discordance is best visualized in the four-chamber plane. In this imaging plane, the septal hinge points of the AV valves are readily appreciated (see Fig. 10.3). In situs solitus of the atria and concordant AV connections, the AV valve associated with the RA and RV will have a septal hinge that is displaced toward the apex when compared to the contralateral valve. In situs solitus of the atria and CCTGA, due to the discordant AV connection, it is the left-sided AV valve hinge point that is closer to the ventricular apex. Additional scans from the apical transducer position can define the anatomy of the AV valves, ventricular morphology, discordant AV connection, and the VA relationships (Fig. 10.7A). In addition, AV valve abnormalities, LV outflow tract obstruction (Fig. 10.7B) and muscular ventricular septal defects (VSDs) can be evaluated.
Figure 10.3. Apical four-chamber view demonstrating anterior–posterior relationship of ventricular septum resulting in a more vertical orientation of the septum and side-by-side relationship of ventricles. Left-sided ventricle is the morphologic right ventricle and right-sided ventricle is the morphologic left ventricle.
Figure 10.4. Pathology specimens. A: Levocardia with normally related great vessels (ventriculoatrial [VA] concordance) and atrioventricular (AV) concordance. B: Congenially corrected transposition of the great arteries with dextrocardia. (From the Dr. William Edwards collection, Mayo Clinic.)
Apical four-chamber imaging is more challenging when the ventricles are positioned in a superior and inferior fashion. In these patients it will not be possible to image both AV valves in the same plane. In this setting, the transducer will need to be tilted inferiorly to see the right-sided mitral valve and superiorly to see the left-sided tricuspid valve. The septal hinge point relationship is more difficult to appreciate. The diagnosis of CCTGA in these patients relies on the other features which define ventricular morphology.
Figure 10.5. Subcostal imaging plane with transducer angulated anterior and superior. Demonstrates the unique anatomy of the left ventricle in CCTGA with the pulmonary outflow tract (arrow) deeply wedged between the right and left atrioventricular valves.
The side-by-side relationship of the ventricles, more vertical orientation of the ventricular septum, and side-by-side relationship of the great arteries all make the parasternal long-axis views in CCTGA confusing. Unlike in the normal heart, the long axis in CCTGA is more vertically oriented (Fig. 10.8). This allows easy confirmation of the parallel arrangement of the great arteries. However, because of the side-by-side relationship of the ventricles, when the transducer is placed in a standard long-axis imaging position, several views are obtained, including a long-axis image through the LV and pulmonary artery (see Fig. 10.8A) and a long-axis image through the morphologic RV and aorta (see Fig. 10.8B). Adding to the confusion, from the same standard long-axis imaging plane, it is also possible to obtain an image through the pulmonary valve and the left AV valve. The membranous septum is thin and often shifted to the right, away from this imaging plane. As a result, this plane can give the false impression that the left AV valve and the posteriorly positioned pulmonary valve are related to the same (left-sided) ventricle. A large ventricular septal defect (VSD) may make this plane of imaging even more challenging. In this setting, the pulmonary valve appears related to both AV valves, creating the appearance of a single ventricle. Nevertheless, the long-axis imaging plane is useful for evaluating the great artery relationships and for detecting the presence of outflow tract obstruction.
The short-axis imaging plane in the setting of CCTGA is also very helpful. The ventricular septum in CCTGA is more horizontally oriented than it is in the normal heart (Fig. 10.9A). At the level of the aortic and pulmonary valves, the relationship of the great arteries can be confirmed. In the majority of cases, the aortic valve will be leftward, anterior, and superior to the pulmonary valve (Fig. 10.9B). With slight superior angulation from the level of the aortic valve, the coronary arteries can be identified (Fig. 10.9C). In 85% of cases, the coronary arteries will be inverted. The coronary artery that arises from the left posterior–facing sinus has the epicardial distribution of a morphologic right coronary artery. Conversely, the coronary artery arising from right posterior–facing sinus has the epicardial distribution of a morphologic left coronary artery and gives rise to an anterior descending branch and a right-sided posterior “circumflex” branch. A single coronary artery is the most common coronary anomaly in CCTGA. With further superior angulation of the transducer, the bifurcation of the PA can be identified. This image confirms the posterior position of the PA (Fig. 10.9D).
Figure 10.6. Subcostal imaging in CCTGA. A: Subcostal coronal image demonstrating the most common form of congenitally corrected transposition of the great arteries (TGA) with the pulmonary veins connected to the left-sided atrium. B: Subcostal coronal imaging with transducer angulated anterior and superior demonstrating that the left atrium (LA) connects to a morphologic right ventricle (RV) and the septal attachments of the left-sided morphologic tricuspid valve (arrows). C: With the transducer angulated even more superior, the relationship of this ventricle to a great artery that arches and then gives rise to coronary arteries (aorta) is identified. D: Subcostal coronal image demonstrating relationship of the right-sided structures. Right-sided atrium drains to morphologic left ventricle that then gives rise to an artery that branches (arrows), the main pulmonary artery.
Figure 10.7. Apical inflow and outflow images of CCTGA. A: Apical four-chamber view demonstrating atrioventricular relationships in the setting of congenitally corrected transposition of the great arteries. B: Apical four-chamber image with transducer angulated anterior and superior to demonstrate the pulmonary outflow tract.
Figure 10.8. Parasternal long-axis images with transducer placed in the standard long-axis imaging position. Demonstrates the two separate long-axis views that can be obtained in congenitally corrected transposition of the great arteries with slight leftward or rightward angulation. A: Long-axis image through the morphologic left ventricle (LV) and pulmonary artery (right). B: Long-axis image through the morphologic right ventricle (RV) and aorta (left).
Figure 10.9. Parasternal imaging in CCTGA. A: Short-axis imaging plane demonstrating that the septum (arrow) in the setting of congenitally corrected transposition of the great arteries (CCTGA) is more horizontal than usual. B: With superior angulation of the transducer, the level of the aortic and pulmonary valves can be imaged allowing confirmation of the relationship of the great arteries (aortic valve leftward, anterior, and superior to pulmonary valve). C: With further superior angulation from the level of the aortic valve, the coronary arteries can be identified (arrows). D: With further superior angulation of the transducer, the bifurcation of the pulmonary artery can be identified confirming its posterior position.
In CCTGA, it is often difficult to image the aortic arch from the standard suprasternal position. In CCTGA, the course of the ascending aorta is straight and leftward. It then arches with the descending aorta coursing downward on the left behind the ascending aorta. As a result, to image the aortic arch and a patent ductus arteriosus in the setting of CCTGA, the transducer needs to be placed in high left parasternal position, similar to the so-called “ductal view.” In this position, it is also important to delineate the brachiocephalic branching pattern of the aortic arch given that a right aortic arch can occur in 18% of CCTGA.
ASSOCIATED CARDIAC LESIONS
Tricuspid valve abnormalities are the most common associated lesions in CCTGA, occurring in 90% of cases at autopsy. These features are best demonstrated in the apical four-chamber view but also can be seen in the subcostal coronal and modified short-axis views. The tricuspid valve is usually dysplastic, with or without displacement of the septal and posterior leaflets. Most commonly, the displacement is mild and does not meet criteria for Ebstein anomaly (Fig. 10.10). When features of Ebstein anomaly are present in CCTGA, typically the anterior leaflet is least affected, with severe involvement of both the septal and posterior leaflets. In the most severe form, there can be an unguarded tricuspid valve orifice with severe regurgitation (Fig. 10.11 A–B). When severe Ebstein anomaly is present, there can be associated RV hypoplasia with subaortic obstruction and coarctation of the aorta. This is rare, but it is always associated with an abnormal tricuspid valve with severe regurgitation and a disordered RV with marked thinning of the myocardium. Rarely, subaortic obstruction can occur with an intact ventricular septum. In these cases, the ascending aorta is usually hypoplastic. The subcostal four-chamber and short-axis imaging planes are useful for evaluating RV outflow tract obstruction. The high left parasternal view is useful for diagnosing coarctation of the aorta. Other associated left AV valve abnormalities include a supravalvular ring and varying degrees of AV valve override and straddling in the setting of a VSD.
Figure 10.10. Apical four-chamber view demonstrating mild inferior displacement of the septal leaflet of the tricuspid valve (arrows) in congenitally corrected transposition of the great arteries.
Figure 10.11. Ebstein-like deformity of the left AV valve in CCTGA. A: Close-up image from the apical four-chamber view demonstrating severe displacement of the septal leaflet of the tricuspid valve (Ebstein features). B: Color image from the same plane demonstrating severe tricuspid valve regurgitation.
Figure 10.12. Apical four-chamber image demonstrating a large membranous ventricular septal defect (VSD) with extension into the inlet septum (asterisk).
A VSD occurs in 60% of patients with CCTGA. They most commonly are large membranous defects with posterior extension into the inlet septum (Figs. 10.12 and 10.13). Because the VSD is posterior it may be partially occluded by the apically displaced septal leaflet of the tricuspid valve or by AV valve tissue that straddles through the defect into the right-sided LV (Fig. 10.14). The short-axis, apical four-chamber, and subcostal imaging planes are useful for identifying these lesions. Posterior straddling of the left AV valve is most common.
LV outflow tract obstruction (subpulmonary stenosis) is identified in 30% to 50% of patients with CCTGA. This usually occurs in the setting of a large VSD. The level of obstruction is typically at the subvalvular level secondary to wedging of the subpulmonary outflow tract between the infundibular septum and the ventricular free wall (Fig. 10.15A). Fibrous tissue from the membranous septum that protrudes into the subpulmonary area contributes to obstruction (Fig. 10.15B–C). Abnormal chordal attachments from the mitral or tricuspid valves exacerbate outflow obstruction. The pulmonary valve may also be dysplastic. Doppler interrogation from the subcostal coronal imaging plane, where flow is parallel to the beam of sound, allows for accurate quantitation of the gradient across the obstruction (Fig. 10.15D). However, given the close proximity to the AV valves and the presence of coexisting AV abnormalities, care must be taken not to confuse the systolic jet of AV regurgitation with LV outflow tract obstruction.
Figure 10.13. Membranous VSD in CCTGA. A: Subcostal imaging demonstrating a large membranous ventricular septal defect extending into inlet septum in setting of congenitally corrected transposition of the great arteries. B: Close-up view demonstrating same anatomy.
In CCTGA, the AV node and the bundle of His have unusual locations and are fragile. While this cannot be imaged by echocardiography, many of these patients do develop complete heart block (1% to 2% per year), necessitating placement of transvenous pacemaker leads that can lead to progressive mitral valve regurgitation (Fig. 10.16). If complete heart block occurs as a fetus, hydrops fetalis can develop and may come to the attention of the fetal sonographer. This situation is rare but the rhythm is readily demonstrated by fetal echocardiography. Figure 10.17A demonstrates the atrial rate in a fetus with complete heart block. In contrast, the simultaneous ventricular rate is much slower (Fig. 10.17B).
Although there have been occasional reports of patients with CCTGA having normal or near normal RV function in their sixth and seventh decades, such a clinical course is extremely rare. In one of the largest series (121 patients) from Texas Children’s Hospital, who were diagnosed with CCTGA at a median age of 1 month (range, 28 months to 48 years), 70% required surgery by age 1.5 years (range, 1 day to 19 years). In this series, the mode of clinical presentation varied by age groups: most neonates presented with cyanosis, whereas infants and older children had congestive heart failure and pulmonary overcirculation. Those patients who were asymptomatic had isolated CCTGA, a small VSD, or mild pulmonary outflow tract obstruction or were hemodynamically well balanced with a VSD and pulmonary outflow tract obstruction. In early childhood, operations included systemic-to-pulmonary artery shunts, pulmonary artery banding, VSD closure with or without pulmonary valvotomy/resection, and tricuspid valve repair/replacement. Following initial surgical intervention, 80% of patients required reintervention, with tricuspid valve repair/replacement or LV-to-pulmonary artery conduit replacement. In operated and unoperated patients with CCTGA, progressive tricuspid valve regurgitation and RV dysfunction remain the greatest long-term risks of morbidity.
Figure 10.14. Membranous septal aneurysm and VSD in CCTGA. A: Subcostal image demonstrating membranous septal tissue protruding through a ventricular septal defect into the pulmonary outflow tract. B: Same subcostal image with color flow imaging demonstrating left-to-right shunting through the ventricular septal defect into the pulmonary outflow tract.
Figure 10.15. Pulmonary outflow tract and subpulmonary stenosis in CCTGA. A: Subcostal image demonstrating typical position of subpulmonary outflow tract deeply wedged between the right and left atrioventricular valves, in the setting of congenially corrected transposition of the great arteries. B:Two-dimensional subcostal image demonstrating membranous septal tissue protruding into pulmonary outflow tract. C: Subcostal color flow image demonstrating aliasing of flow below the valve at the level of membranous septal tissue. D:Continuous-wave Doppler signal from same imaging plane, demonstrating significant fixed subpulmonary obstruction.
Figure 10.16. Pacemaker-induced right AV valve regurgitation. A: Pathology specimen demonstrating a transvenous pacemaker wire crossing the mitral valve into the morphologic left ventricle. B: Two-dimensional image from the apical four-chamber plane demonstrating a pacer wire crossing mitral valve into the morphologic left ventricle. C: Color flow image from same plane demonstrating mitral regurgitation (arrows) along pacemaker lead (A, From the Dr. William Edwards collection, Mayo Clinic).
Figure 10.17. M-mode tracings of atrial and ventricular wall motion in a fetus with complete heart block. A: Determination of the atrial rate: The A to A interval is 425 milliseconds (ms), predicting an atrial rate of 141 beats per minute (bpm). B: Determination of the ventricular rate: The V to V interval is 1068 ms, predicting a ventricular rate of only 56 bpm. The intervals are distinctly different, indicating dissociation between the atria and ventricles (complete heart block).
The long-term risk for progressive RV dysfunction and tricuspid regurgitation in CCTGA has led some to promote the concept of an “anatomic repair” (double-switch operation) that incorporates the LV into the systemic circulation. This therapeutic concept was first introduced in 1990. The anatomic repair is accomplished by using an atrial switch procedure (either Mustard or Senning), and a concurrent arterial switch procedure (Fig. 10.18). In those patients with pulmonary outflow tract obstruction and a VSD, the LV is tunneled through the VSD to the aorta by patch material and the RV is connected to the pulmonary artery by a valved conduit (a combination of Mustard- and Rastelli-type–operations) (Fig. 10.19A). Another modification is to perform a bidirectional cavopulmonary connection in conjunction with a “hemi-Mustard” (inferior vena cava flow baffled to the left-sided tricuspid valve and an arterial switch) (Fig. 10.19B–C). In older patients, the LV has to be prepared to function as the systemic ventricle. In the absence of pulmonary outflow tract obstruction, this requires placement of a pulmonary artery band in an effort to raise the LV pressure and induce hypertrophy. Echocardiographic assessment is a critical part of this process in the operating room to ensure proper band position and during the postoperative period to assess LV preparation and remodeling. While initial promising results were published, the retraining of the LV has not been consistently effective except in young infants. Most centers have abandoned the “double switch” for older patients with unprepared LVs; however, it remains an attractive approach for young infants, especially when severe tricuspid valve dysplasia is present. The double switch provides an opportunity to remove the dysplastic tricuspid valve from the systemic circulation and restores the LV as the systemic pump.
In addition to training the subpulmonic LV, placement of a pulmonary band in CCTGA has been performed as treatment for severe symptomatic tricuspid regurgitation. This technique is typically reserved for those patients with severe tricuspid regurgitation and severely reduced systemic RV function, who are not surgical candidates other than for transplantation. This technique has resulted in varying outcomes (Fig. 10.20A–B). In theory, placement of the pulmonary band increases the subpulmonic LV pressure, resulting in alteration of the ventricular septal position (septal shift) and improved tricuspid valve leaflet coaptation. Experience with this technique remains limited to only a few centers but does hold promise for patients with few other clinical options.
Figure 10.18. Diagram depicting a double switch operation for congenitally corrected transposition of the great arteries. This procedure incorporates elements of both an atrial switch operation (Mustard) and an arterial switch (Jatene). (From DiBardino DJ, et al. The hemi-Mustard, bidirectional Glenn, and Rastelli operations used for correction of congenitally corrected transposition, achieving a “ventricle and a half repair.” Cardiol Young 2004;14:330–2.)
ASSESSMENT OF THE SYSTEMIC RIGHT VENTRICLE
Many patients with CCTGA will develop RV dysfunction and tricuspid valve regurgitation over time, making quantification of function and tricuspid regurgitation crucial components of the echocardiographic evaluation of these patients. Although the definition of “normal” systemic RV ejection fraction remains debated, most authorities agree that an ejection fraction of 50% or greater is normal. Assessing the function of the morphologic RV, however, is challenging because of its complex anatomy. Difficulties are compounded by irregularities in the ventricular cavities and wall motion abnormalities in patients with congenital heart lesions. None of the geometric assumptions used to assess LV function hold true for the systemic RV. Unlike the LV with both deep circumferential and longitudinal myocardial fibers, the majority of the right ventricular myocardial fibers originate at the apex of the heart and insert into the right AV junction, such that the bulk of the RV myocardium is composed of longitudinally arranged fibers. This complex myocardial fiber arrangement and shape of the RV make quantification difficult. Therefore, most centers rely on crude visual estimation of RV systolic function.
Figure 10.19. Double Switch Operation (Mustard-Rastelli–type). A: Diagram depicting a modification of the double switch operation (Mustard-Rastelli–type) used in patients with pulmonary/subpulmonary obstruction. Flow from the morphologic left ventricle (LV) is baffled via the ventricular septal defect (VSD) to the aorta. A conduit is placed to direct morphologic right ventricular (RV) blood to the pulmonary artery. An atrial switch operation is also performed. B: Diagram depicting a modification of the double switch operation (hemi-Mustard) in which only the inferior vena cava (IVC) flow is baffled to the morphologic right ventricle and tricuspid valve (TV). Superior vena cava (SVC) is diverted to the pulmonary artery via a bidirectional Glenn. Pulmonary venous blood passes behind the IVC baffle to enter the mitral valve (MV). An arterial switch is also performed. C: Apical four-chamber image in a child after a double switch operation. A widely patent pulmonary venous baffle is demonstrated. (From DiBardino DJ, et al. The hemi-Mustard, bidirectional Glenn, and Rastelli operations used for correction of congenitally corrected transposition, achieving a “ventricle and a half repair.” Cardiol Young2004;14:330-2.)
Figure 10.20. Pulmonary artery banding and its impact on systemic atrioventricular valve regurgitation in CCTGA. A: Before placement of a pulmonary artery band, this patient had severe tricuspid valve regurgitation. B: In the same patient, after pulmonary artery band placement, the morphologic LV pressure increase causes a leftward shift of the ventricular septum, thereby reducing the amount of tricuspid regurgitation.
As a result of the difficulties with visual estimation of systemic RV function, newer techniques have gained growing acceptance in clinical practice. Many of these methods are described elsewhere in this textbook. The myocardial performance index was first described by Tei and colleagues as a measure of combined systolic and diastolic function of the RV. Since then, this index has been used to assess the systemic RV and in theory is independent of geometric assumptions. Preliminary data indicate a strong negative correlation between the RV myocardial performance index and the calculated ejection fraction by cardiac MRI. In one of the early studies to evaluate this, the mean myocardial performance index for patients with normal systemic RV function by cardiac MRI (ejection fraction 50% or greater) was 0.29 6 0.08 (range, 0.21 to 0.43). This value is similar to the normal value for a systemic LV (0.34 to 0.40). As systemic RV function decreases, the myocardial performance index continues to increase. Most patients with decreased RV function and tricuspid regurgitation have an RV myocardial performance index score .0.72 6 0.17.
Other techniques that have been used to evaluate systemic RV function include measuring isovolumic myocardial acceleration (IVA) during isovolumic contraction using tissue Doppler imaging or velocity vector imaging. IVA has been shown in several small studies to be a reliable technique to measure longitudinal systemic RV function. Compared with subpulmonic RVs and systemic LVs, the IVA in systemic RVs is lower (mean: systemic RV, 1.0 6 0.4; systemic LV, 1.4 6 0.5; subpulmonic RV, 1.8 6 0.6). Compared with other techniques, IVA may also provide the advantage of being less dependent on changes in preload and afterload.
Finally, because the bulk of the RV myocardium is composed of longitudinal fibers, many researchers have proposed techniques to evaluate the longitudinal performance of the systemic RV. One of the earliest techniques was to measure the RV AV ring excursion using M-mode traces taken from the apical four-chamber view with the cursor positioned through the lateral angles of the tricuspid and mitral valves. Compared with systemic LVs and subpulmonic RVs, the total AV ring excursion has been shown to be lower in patients with CCTGA. Most recently, studies have focused on using strain, strain rate, and myocardial systolic and diastolic velocities to quantify longitudinal function. Preliminary data indicate that for both the systemic RV and the subpulmonic RV, the dominant myocardial motion is longitudinal. The greatest displacement, myocardial systolic and diastolic velocities, and strain to be measured are at the RV basal septal and free walls.
Quantifying systemic tricuspid valve regurgitation can also be a challenge. In general, techniques to quantify mitral regurgitation have been applied to the systemic tricuspid valve. Clinical correlation of these techniques in the setting of CCTGA is limited. Vena contracta width by color flow mapping appears to be one of the most reliable techniques with the majority of patients with severe regurgitation having a vena contracta width of 7 mm or greater. Other findings suggestive of severe systemic tricuspid regurgitation include (a) pulmonary vein systolic flow reversals, (b) color flow area of 40% of LA size or greater, (c) annulus dilation or inadequate cusp coaptation, (d) increased tricuspid valve Doppler inflow E velocity of 1.5 m/s or greater, (e) effective regurgitant orifice of 0.40 cm2 or greater, (f) regurgitation fraction greater than 55%, and (g) regurgitation volume of 60 mL or greater.
Finally, because complete heart block is common in patients with CCTGA, many patients will have placement of transvenous pacemaker systems. While this is often necessary to avoid complications associated with heart block, insertion of a pacemaker may precipitate deterioration in systemic ventricular function by altering the position of the septum leading to failure of tricuspid valve leaflet coaptation and worsening regurgitation. When systemic RV dysfunction develops after placement of a transvenous system, many centers are now attempting to place biventricular pacing systems (cardiac resynchronization). The theory behind this maneuver is that biventricular pacing may help alleviate ventricular mechanical dyssynchrony and improve regurgitation and ventricular function. The detection of mechanical dyssynchrony involves the use of Doppler tissue imaging, velocity vector imaging, or strain and strain imaging. Unfortunately, the experience of cardiac resynchronization in all congenital heart disease remains limited to case series and small experimental crossover studies in the acute postoperative setting. Access to the coronary sinus is important for placement of the biventricular pacing system. The echocardiographer may be called on to assist in identifying the orifice of the coronary sinus. In patients with a systemic RV, echocardiographers should routinely evaluate the location and course of the coronary sinus.
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1.Which is the most common coronary artery anomaly in CC-TGA?
A.LAD from the RCA
B.LAD from the circumflex
C.Single coronary artery
D.RCA from the right anterior sinus
2.Which cardiac rhythm or conduction problem is most common in a 10-year-old with CC-TGA?
A.Right bundle branch block
D.Complete heart block
3.In CC-TGA, which is the most common orientation of the great arteries?
A.Aorta anterior and right of PA
B.Aorta anterior and left of PA
C.Aorta posterior and right of PA
D.Aorta posterior and left of PA
4.What percentage of patients with CC-TGA have a VSD?
5.What is the most common location for the VSD in CC-TGA?
6.In CC-TGA, which of the following is TRUE?
A.Tricuspid valve connects to the morphologic LV
B.RV has no moderator band
C.Mitral valve is in fibrous continuity with pulmonary valve
D.Aorta is posterior and rightward of the PA
7.The double-switch operation is most useful in which situation?
A.d-TGA with intact ventricular septum
B.d-TGA with a VSD
C.CC-TGA with no associated cardiac lesions
D.CC-TGA with severe Ebstein malformation
8.A morphologic RV can be defined by all of the following EXCEPT:
A.apical displacement of the hinge point of the tricuspid septal leaflet.
B.a tricuspid (three-leaflet) atrioventricular valve.
C.a moderator band.
D.fibrous continuity of the atrioventricular and semilunar valves.
9.Which of the following is most common in CC-TGA?
A.Right aortic arch
10.Which imaging plane is best suited to evaluate AV discordance in CC-TGA?
1.Answer: C. A single coronary artery is the most common anomaly in CC-TGA. In 85% of cases, the coronary arteries will be inverted. The coronary artery that arises from the left posterior facing sinus has the epicardial distribution of a morphologic right coronary artery. Conversely, the coronary artery arising from right posterior facing sinus has the epicardial distribution of a morphologic left coronary artery, and gives rise to an anterior descending branch and a right-sided posterior “circumflex.”
2.Answer: D. Patients with CC-TGA may be born with complete heart block or develop it at a rate of approximately 1-2% per year.
3.Answer: B. The most common position of the aorta in CC-TGA is anterior and leftward of the PA. More rarely, the aorta can be directly anterior or anterior and rightward of the PA.
4.Answer: C. Other than anomalies of the systemic tricuspid valve, VSD is the most common associated lesion in CC-TGA. The majority (60%) of patients will have one.
5.Answer: A. The most common location for a VSD in CC-TGA is a large membranous defect with posterior extension into the inlet septum. This enables prolapse of chordal tissue from the atrioventricular valves through the defect.
6.Answer: C. In all four chambered hearts, the tricuspid valve connects to the RV and the mitral valve connects to the LV. A morphologic LV usually has fibrous continuity of the mitral valve with the semilunar valve (the pulmonary valve in the case of CC-TGA), except in cases of double-outlet RV, where mitral-semilunar valve fibrous continuity may be disrupted.
7.Answer: D. The double-switch operation is most useful in small children with CC-TGA and a severely dysplastic systemic atrioventricular valve. Patients with d-TGA require a neonatal arterial switch operation.
8.Answer: D. Fibrous continuity of the mitral valve and semilunar valve is a typical characteristic of LV morphology. The other features listed are typical of RV morphology. The infundibulum of the RV separates the tricuspid valve from the semilunar valve.
9.Answer: D. LVOT obstruction due to pulmonary valve or subvalve stenosis occurs in 30-50% of patients with CC-TGA. Right aortic arch occurs in 18% of CC-TGA, dextrocardia, or mesocardia in 25% of CC-TGA, and primum ASD is rare.
10.Answer: A. The apical four-chamber imaging plane permits assessment of the most consistent intracardiac landmark, the cardiac crux. Atrioventricular valve apical displacement is determined in this view. The parasternal and suprasternal notch views in CC-TGA require unique angulation techniques and yield multiple important views of ventriculo-arterial and great artery relationships.