Congenitally Corrected Transposition of the Great Arteries

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Chapter 6 Congenitally Corrected Transposition of the Great Arteries

More than a century elapsed before Karl von Rokitansky ¹ applied the term corrected to a hitherto undescribed form of transposition of the great arteries: “The left atrioventricular valve and the left-sided ventricle resembled the usual right atrioventricular valve and right ventricle. The aorta is positioned somewhat left and anterior…. The right-sided ventricle … is finely trabeculated, as usually seen in the left-sided ventricle. The venous atrioventricular ostium has a bivalve. From the right-sided ventricle arises a somewhat right and posteriorly positioned pulmonary artery…. The atria are normal, a right caval atrium and a left pulmonary venous atrium.”

At the end of the 18th century, Mathew Baille ² described a singular malformation characterized by discordant origins of the arterial trunks from the ventricular mass. In 1957, Anderson and coworkers described the clinical manifestations of Rokitansky’s singular malformation; and 4 years later, Schiebler and coworkers³ changed the term corrected to congenitally corrected to clarify that the correction was a gift of God and not a gift of the surgeon. The reader is referred to three seminal publications.⁴^–⁶

Transposition of the great arteries is characterized by chambers that are joined concordantly at the atrioventricular junction but discordantly at the ventriculo-great arterial junction (see Chapter 27).⁷^,⁸ The pulmonary artery arises from a morphologic left ventricle, and the aorta arises from a morphologic right ventricle. The circulations are in parallel rather than in series. Congenitally corrected transposition is characterized by chambers that are joined discordantly at the atrioventricular junction and ventricles that are joined discordantly at the ventriculo-great arterial junction; atrioventricular alignments and ventriculoarterial alignments are both discordant (Figures 6-1 and 6-2).³^,⁴^,⁹ The double discordance—atrioventricular and ventriculoarterial—physiologically corrects the discordance intrinsic to each (see Figure 6-1). Blood from a morphologic right atrium reaches the pulmonary artery by traversing a morphologic mitral valve and a morphologic left ventricle, and blood from a morphologic left atrium reaches the aorta by traversing a morphologic tricuspid valve and a morphologic right ventricle (Figures 6-1 and 6-3).³^,⁴^,⁹ The terms atrioventricular discordance, l-transposition, ventricular inversion, and congenitally corrected transposition are used interchangeably. Atrioventricular discordance requires the presence of two morphologically distinct atria and two morphologically distinct ventricles. Hearts in which two morphologically distinct atria are aligned with one ventricle (univentricular atrioventricular connection) are the subject of Chapter 26.

Figure 6-1 A, Gross specimen of congenitally corrected transposition of the great arteries illustrates ventriculoarterial discordance. The pulmonary trunk originates from the morphologic left ventricle (LV) and the aorta (Ao) originates from the morphologic right ventricle (RV). B and C, Illustrations of congenitally corrected transposition of the great arteries for comparison with the normal heart. Congenitally corrected transposition is characterized by atrioventricular discordance and ventriculoarterial discordance. Blood from a morphologic right atrium (RA) traverses a morphologic mitral valve into a morphologic left ventricle (LV) and then enters a pulmonary trunk (PT) that is rightward and posterior. Blood from a morphologic left atrium (LA) traverses a morphologic tricuspid valve into a morphologic right ventricle (RV) and then enters an aorta (Ao) that is leftward and anterior. The double discordance means that right atrial blood finds its way into the pulmonary artery and left atrial blood finds its way into the aorta. Anatomic transposition of the great arteries is physiologically corrected. The great arteries run parallel to each other and do not cross as in the normal heart. Coexisting anomalies include a malformed left atrioventricular valve, a ventricular septal defect, and pulmonary stenosis. B, The normal heart is characterized by atrioventricular concordance, ventriculoarterial concordance, and a pulmonary artery that crosses anterior to the aorta.

Figure 6-2 Angiocardiograms (anteroposterior) from a 34-year-old man with congenitally corrected transposition of the great arteries and a moderately incompetent left atrioventricular valve. A, Contrast material opacifies a morphologic left ventricle (MLV) from which a rightward and posterior pulmonary trunk arises (PT). B, Contrast material outlines a hump-shaped crescent morphologic right ventricle (MRV) from which a leftward and anterior ascending aorta (Ao) arises. Catheters in the pulmonary trunk and ascending aorta run parallel to each other and do not cross. The left atrium (LA) opacifies because of left atrioventricular valve regurgitation.

Figure 6-3 Simplified schematic illustration of the circulation in congenitally corrected transposition of the great arteries.

The terms used in this chapter were defined in Chapter 3 but are repeated here for the reader’s convenience.

Transposition: Discordant origin of the arterial trunks from the ventricular mass. The aorta arises discordantly from a morphologic right ventricle, and the pulmonary trunk arises discordantly from a morphologic left ventricle. The pulmonary circulation and the systemic circulations are in parallel.

Congenitally corrected transposition: A morphologic right atrium is discordantly aligned with a morphologic left ventricle from which the pulmonary artery arises, and a morphologic left atrium is discordantly aligned with a morphologic right ventricle from which the aorta arises (see Figures 6-1 and 6-3). Systemic venous blood from the right atrium finds its way into the pulmonary artery, and pulmonary venous blood from the left atrium finds its way into the aorta, so the circulation is physiologically corrected. The pulmonary circulation and the systemic circulations are in series.

Ventricular inversion refers to atrioventricular discordance with ventriculoarterial concordance. A morphologic right atrium is aligned with a morphologic left ventricle that gives rise to the aorta, and a morphologic left atrium is aligned with a morphologic right ventricle that gives rise to the pulmonary trunk.¹⁰^,¹¹

l-Transposition: An l-loop in situs solitus. The sinus or inflow portion of the morphologic right ventricle is to the left of the morphologic left ventricle.

Inversion: Reversal of position but not mirror image. Ventricular inversion refers to a morphologic left ventricle in the right side of the heart and a morphologic right ventricle in the left side of the heart. Morphologic tricuspid and mitral valves are concordant with morphologic right and left ventricles, so inversion of the ventricles implies inversion of the atrioventricular valves. Isolated infundibuloarterial inversion is a rare anomaly in which the infundibulum and great arteries are inverted but the atria and ventricles are not inverted.¹² The inverted pulmonary trunk and its subpulmonary infundibulun originate from the morphologic left ventricle, and the inverted aorta originates from a morphologic right ventricle, so the physiology of the circulation is analogous to complete transposition of the great arteries (see Chapter 27).

Chamber designations: Right atrium and left atrium and right ventricle and left ventricle refer to anatomic (morphologic) characteristics, not to position.

The great arteries: The ascending aorta and pulmonary trunk are defined by their ventricle of origin and by their lateral and anteroposterior spatial relationships.

d-Loop: Refers to the normal rightward (dextro = d) bend or loop in the developing straight heart tube of the embryo; indicates that the sinus or inflow portion of the morphologic right ventricle lies to the right of the morphologic left ventricle.

l-Loop: Refers to a leftward (levo = l) bend or loop in the straight heart tube of the embryo; indicates that the sinus or inflow portion of the morphologic right ventricle lies to the left of the morphologic left ventricle.

Concordant: Harmonious, appropriate.

Discordant: Disharmonious, inappropriate.

Discordant loop: An l-loop in situs solitus and a d-loop in situs inversus.

Atrioventricular discordance: Alignment of a morphologic right atrium with a morphologic left ventricle and alignment of a morphologic left atrium with a morphologic right ventricle.

Ventriculoarterial discordance: Origin of the pulmonary trunk from a morphologic left ventricle and origin of the aorta from a morphologic right ventricle.

Criss-cross hearts: Described by Lev and Rowlatt in 1961 ¹³ and so-named by Anderson, Shinebourne, and Gerlis in 1974.¹⁴ In normal hearts, the atrioventricular connections (inflow tracts) are parallel to each other when viewed from the front. In criss-cross hearts, the atrioventricular connections are not parallel but are angulated as much as 90 degrees.¹⁴ Criss-cross hearts result from abnormal rotation of the ventricular mass around its long axis, resulting in relationships that could not be inferred from the inflow tracts. Several types of criss cross hearts exist. Those with discordant atrioventricular alignments and concordant ventriculoarterial alignments are called isolated ventricular inversion (see previous discussion). The physiology of the circulation is analogous to complete transposition of the great arteries.¹⁰ Criss-cross hearts with ventricles that are in a superoinferior or upstairs-downstairs relationship reflect rotation of the ventricular mass along its horizontal. Criss-cross hearts and superoinferior ventricles may coexist (Figure 6-31) or occur separately. Morphologic patterns in criss-cross hearts include deficiency of the subpulmonary infundibulum, subpulmonary stenosis, a subaortic infundibulum, a nonrestrictive ventricular septal defect, and visceroatrial situs solitus.¹⁵

Segmental approach: Analysis according to the heart’s three major developmental segments: 1, visceroatrial situs; 2, ventricular loop; and 3, conotruncus. The atrioventricular valves and the infundibulum are the two connecting cardiac segments.

Figure 6-31 Echocardiograms (subcostal) in a criss-cross heart with superoinferior ventricles. A, The superior vena cava (SVC) joins a morphologic right atrium (RA) aligned with a concordant morphologic right ventricle (MRV) that is superior and to the left of a morphologic left ventricle (MLV). The tricuspid valve (TV) has a right-to-left orientation. B, Two pulmonary veins (PV; arrows) join the morphologic left atrium (LA), which is aligned with an inferior and rightward morphologic left ventricle (MLV). Atrioventricular concordance with ventriculoarterial discordance resulted in the physiology of complete transposition of the great arteries.

Congenitally corrected transposition of the great arteries typically occurs in situs solitus. The estimated prevalence rate is 0.5% of clinically diagnosed congenital malformations of the heart or approximately 1 in 13,000 live births.¹⁶^,¹⁷ Virtually all patients have coexisting cardiac malformations—ventricular septal defect, pulmonary stenosis, abnormalities of the left atrioventricular (AV) valve, and conduction defects.

The coronary artery arrangement is an important morphologic aspect of congenitally corrected transposition.⁷ The Leiden Convention proposed a means of relating the origins of the coronary arteries to the aortic sinuses from which they originate.⁷^,¹⁸ The coronary arteries almost always arise from both, or one or the other, aortic sinuses that are adjacent to the pulmonary trunk⁷ and are morphologically concordant with the ventricles (i.e., the right coronary artery perfuses the morphologic right ventricle and the left coronary artery perfuses the morphologic left ventricle; Figure 6-4; see Chapter 32).³^,⁴^,¹⁹^–²² Epicardial distribution is a guide to ventricular inversion because the course of the anterior descending artery establishes the location of the ventricular septum. Coronary artery abnormalities are common,²² especially a single coronary artery (see Chapter 32).²⁰

Figure 6-4 Coronary arteriograms from a 41-year-old man with congenitally corrected transposition of the great arteries. A, The left anterior oblique shows a morphologic left coronary artery (LCA) concordant with a morphologic left ventricle. B, The right anterior oblique shows a morphologic right coronary artery (RCA) concordant with a morphologic right ventricle.

In congenitally corrected transposition of the great arteries, the anterior and leftward ascending aorta and the posterior and rightward pulmonary trunk are parallel and do not cross as in the normal heart ³ (see Figures 6-1 and 6-2). The aorta is either convex to the left or ascends vertically but is not border forming on the right. A subaortic conus is responsible for the anterior and leftward position of the ascending aorta and the posterior and medial position of the pulmonary trunk.²³ Anatomically corrected malposition refers to an anomaly in which the ascending aorta lies anterior and to the left of the pulmonary trunk in the presence of atrioventricular and ventriculoarterial concordance.^23,²⁴

The embryologic basis held responsible for atrioventricular discordance in congenitally corrected transposition resides in the ventricular l-loop of the embryonic heart tube. When the heart tube bends to the left in situs solitus, the morphologic right ventricle lies to the left of the morphologic left ventricle. The developing left atrium becomes aligned with the morphologic right ventricle, and the developing right atrium becomes aligned with the morphologic left ventricle. Ventriculoarterial discordance has a less well-defined embryologic basis, with one school of thought arguing that the developmental fault is in the infundibular segment of the embryonic heart tube and the other school arguing that the fault lies in the arterial segment of the embryonic heart tube.

The physiologic consequences of congenitally corrected transposition depend on the functional adequacy of a subaortic morphologic right ventricle and on coexisting congenital malformations.⁴^,¹⁶^,²⁵ The thick-walled subaortic right ventricle is concordant with a right coronary artery that is designed to perfuse a thin-walled low-resistance right ventricle. A normal subpulmonary right ventricle is designed to serve the low-resistance pulmonary circulation, and its geometry remains unchanged when it is inverted to the subaortic position. Regional strain, twist, and radial wall motion in a subaortic right ventricle differ considerably from a subaortic left ventricle.²⁶ An inverted subaortic right ventricle has a high prevalence of myocardial perfusion defects and abnormalities of regional wall motion.²⁷ A normal subpulmonary right ventricle has a relatively high end-diastolic volume, so normal stroke volumes are achieved with ejection fractions of 35% to 45%.¹⁶^,²⁵ Importantly, the low ejection fraction does not increase when a morphologic right ventricle is inverted into the subaortic position, so the ejection fraction is considerably less than that of a normal subaortic left ventricle¹⁶^,²⁵ and response to supine exercise is similar to the response of a noninverted right ventricle.¹⁶^,²⁵ Ventricular septal defect, pulmonary stenosis, abnormalities of the left AV valve, and conduction defects have a considerable impact on the function of an inherently inadequate inverted right ventricle.³^,⁴

A ventricular septal defect is present in 78% of necropsy cases (Figure 6-5), is usually nonrestrictive perimembranous, and typically extends into the inlet and trabecular septum.⁴ The inlet septum is poorly aligned with the atrial septum, which results in a malalignment gap that is sometimes filled by tissue from the membranous septum. Pulmonary stenosis or atresia occurs in 50% of cases and represents obstruction to outflow of the morphologic left ventricle.⁴ The stenosis is isolated in about 20% of cases and occurs with a ventricular septal defect in the remaining 80%. Fixed subpulmonary stenosis⁴ takes several forms: (1) a fibrous subpulmonary diaphragm attached to the mitral valve, analogous to fixed subaortic stenosis in hearts with noninverted ventricles; (2) aneurysms or fibrous tissue tags that originate from the relatively large membranous septum; and (3) accessory mitral leaflet tissue.³ Subaortic stenosis (obstruction to outflow of the morphologic right ventricle) is caused by anterior deviation of the infundibulum septum or by hypertrophied infundibular muscle bundles.¹

Figure 6-5 Angiocardiogram from a 4-year-old boy with congenitally corrected transposition of the great arteries and a nonrestrictive ventricular septal defect. The systemic ventricle has the shape and the coarse trabecular pattern of a morphologic right ventricle (MRV) and gives rise to an ascending aorta (Ao) that is convex to the left. An enlarged pulmonary trunk (PT) is visualized via the ventricular septal defect.

Abnormalities of the inverted left atrioventricular valve are present in more than 90% of cases.⁴ The malformed valve usually functions normally in early life, but an age-related increase in regurgitation is seen. The abnormalities resemble those of Ebstein’s anomaly of a right-sided tricuspid valve in hearts without ventricular inversion (Figure 6-6A),³^,⁴^,²⁸ but the anterior leaflet of the inverted Ebstein’s valve is usually small and malformed²⁸ and the atrialized portion of the inverted right ventricle is poorly developed.²⁸ Left atrioventricular valve incompetence is not necessarily caused by an Ebstein’s-like malformation, and the valve is occasionally stenotic rather than incompetent (see Chapter 13). Neonates with severe regurgitation of the inverted atrioventricular valve have an increased incidence of hypoplastic aortic arch, aortic atresia, and aortic coarctation.²⁹ Abnormalities of the right-sided inverted mitral valve have been reported in more than half of necropsy specimens and consist of multiple cusps, multiple or compound papillary muscles, anomalous chordal attachments, and a cleft valve or a common valve.³⁰

Figure 6-6 A, Angiocardiogram with contrast material injected into the small morphologic right ventricle (MRV) of a 7-month-old male with congenitally corrected transposition of the great arteries and severe incompetence of the left atrioventricular valve. Regurgitant flow opacifies a huge left atrium (LA). The ascending aorta (AAo) originates from the morphologic right ventricle, is convex to the left, and continues as a right-sided descending aorta (DAo). B, Angiocardiogram with contrast material injected into the morphologic left ventricle (MLV) of a 4-year-old boy with congenitally corrected transposition of the great arteries and no coexisting malformations. The plane of the interventricular septum (IVS) is vertical and close to the left sternal border. The morphologic left ventricle is finely trabeculated and gives rise to a rightward and posterior pulmonary trunk (PT) with right and left branches at the same level.

History

The male:female ratio is approximately 1.5:1.³ The occurrence of congenitally corrected transposition and complete transposition among first-degree relatives in different families is believed to represent monogenic transmission and implies a pathogenetic link between the two malformations.³¹^,³² Symptoms and clinical course depend chiefly on the presence and degree of coexisting malformations (see previous discussion), but longevity principally hinges on the vulnerability of the subaortic morphologic right ventricle, even with no coexisting malformations.³³^–³⁵ Infant mortality is related to congestive heart failure. Survival is then relatively constant, with an attrition rate of approximately 1% to 2% year.³⁶ Young patients with isolated congenitally corrected transposition are often overlooked because symptoms are absent and clinical signs are subtle.³ The diagnosis may come to light because of abnormalities in an x-ray (Figure 6-7) or an electrocardiogram (Figure 6-20) or because of symptomatic complete heart block (Figure 6-8).³^,³⁷^,³⁸ High-degree heart block rarely occurs in utero but is occasionally present shortly after birth (see Figure 6-8),³⁹^,⁴⁰ or may announce itself later as a Stokes-Adams attack or sudden death.³⁹^,⁴¹ The age-related risk of development of complete heart block is about 2% per year.³⁹ Left atrioventricular valve regurgitation is closely coupled to long-term survival.³⁶^,³⁸ The regurgitation is usually occult in infants, so late appearance prompts a mistaken diagnosis of acquired mitral regurgitation.