A 45-year-old woman is referred to cardiology for a murmur and abnormal echocardiogram. She had overall a healthy life. She had 3 uncomplicated pregnancies. Although she does not exercise regularly, she had always been able to keep up with her peers. She denied chest pain, shortness of breath or palpitations. At her most recent annual physical examination, her primary care physician auscultated a holosystolic murmur at the apex and at the left sternal border. He referred her for an echocardiogram and subsequently to cardiology for further evaluation. Her past medical history included an appendectomy and well-controlled hypertension with a single drug (thiazide diuretic). She has been a lifelong nonsmoker, works as a second-grade teacher, lives with her husband and has a youngest child in college. Her physical examination revealed a blood pressure of 126/80 mm Hg, heart rate 65 bpm with normal saturations on room air. She had a diffuse apical impulse, 2/6 holosystolic murmur at the apex, radiating to the left sternal border, normal pulses, and no edema on her cardiovascular examination. There were clear lungs and no jugular venous distension. There was no evidence of hepatosplenomegaly on abdominal examination. Echocardiography revealed congenitally corrected transposition of the great arteries (CC-TGA) (with ventricular inversion) with moderate systemic atrioventricular valve regurgitation.
A 2-month old infant presents for a routine visit. He was born at term to a G1, now P1 mother. His mother reported difficulty and diaphoresis with feeds. His birth weight was 7 lb 4 oz. Current weight was 8 lb 14 oz (<3 percentile). His pediatrician auscultated a murmur and refers to pediatric cardiology for further evaluation. On physical examination the infant appears to be thin, mildly ill-appearing infant but in no acute distress. O2 saturations were 88% on room air. On cardiovascular examination, the infant had a soft holosystolic murmur at left lower sternal border and a harsh systolic ejection murmur at the right upper sternal border. The liver was 3 cm below the right costal margin. He had normal pulses and clear lungs. Echocardiography revealed the underlying diagnosis of CC-TGA with a ventricular septal defect and pulmonary valve stenosis.
These 2 cases represent the extremes at which CC-TGA, also known as L-TGA or ventricular inversion, can present.
Patients with isolated CC-TGA are frequently diagnosed due to an abnormal chest x-ray (CXR), electrocardiography (ECG), development of a murmur, or rarely with the development of complete heart block.
Presentation in middle age or beyond is not uncommon, and overall prognosis in these patients is excellent.
Patients who have other associated cardiac anomalies, such as the infant in Case 2 with a ventricular septal defect and pulmonary stenosis, present at a younger age with a much more variable course.
Management of the entire spectrum of CC-TGA is complicated by a lack of quality data to guide appropriate therapeutic options.
CC-TGA occurs in approximately 1 in 13,000 live births.
Male to female ratio is approximately 1.5:1.
Typically, CC-TGA occurs in situs solitus, which means the apex of the heart points to the left, the liver is on the right, and the stomach is on the left.
Prior studies have suggested 90-99% of patients have coexisting cardiac malformations, including ventricular septal defect, pulmonary stenosis, and malformations of the systemic atrioventricular (AV) (tricuspid) valve.1
Complete heart block is thought to occur at a rate of 2% per year.
To understand CC-TGA, and its complications, it is necessary to completely understand the anatomy.
In congenital heart disease, the labels of “left” and “right” ventricle more commonly describe their morphology rather than position in a particular patient.
The “left” ventricle is a thick-walled, cone-shaped structure.
The “right” ventricle is thin-walled, banana-shaped structure that wraps around the left ventricle (LV) which is often not well suited to heavy work-loads.
The mitral valve is always associated with the left ventricle.
The tricuspid valve (TV) is always associated with the right ventricle (RV).
In a normal heart, blood flows from the body to the right atrium, across the tricuspid valve, through the right ventricle and out to the lungs (Figure 6-1A). After becoming oxygenated, blood returns to the left atrium, crosses the mitral valve, through the left ventricle and out the aorta back to the body.
In CC-TGA, there is atrioventricular discordance and ventricular arterial discordance (Figure 6-1B).
Deoxygenated blood from the body enters the right atrium normally; however, because of the atrioventricular discordance, it crosses the mitral valve into the left ventricle.
The ventricular arterial discordance means that the blood is pumped from the left ventricle to the pulmonary artery.
After becoming oxygenated, the blood returns to the left atrium.
Again the atrioventricular discordance means the blood crosses a tricuspid valve into the right ventricle.
Because of the ventricular arterial discordance, the blood is then pumped from the right ventricle to the aorta.
The aorta and pulmonary artery are roughly parallel as they depart the heart. The aorta is anterior and leftward.
The conduction system consists of inverted bundle branches and an anomalous anterior atrioventricular node with a bundle that penetrates the atrioventricular fibrous annulus. This bundle is well formed in young children, but replaced by fibrous tissue beginning in adolescence. The sinus node is positioned normally but the anatomic situation precludes normal conduction because the AV conduction tissue is profoundly abnormal. The normal AV node cannot give rise to the penetrating AV bundle. An anomalous second AV node is the functional AV conduction system in many patients, generally located beneath the opening of the right atrial appendage at the lateral margin between the pulmonic valve and the mitral valve; thus, the node has an anterior position and gives rise to the AV bundle immediately underneath the right anterior pulmonic valve leaflet. This accessory node is not always present and may be hypoplastic or nonfunctional.2
Left ventricular outflow tract obstruction (pulmonary outflow tract) occurs in 30% to 50% of patients and is typically associated with a ventricular septal defect, with approximately one-third of patients also having tricuspid valve deformities.3
The most common anatomic associations include the presence of a ventricular septal defect (VSD), which may be observed in almost 80% of cases (Figure 6-2) and the presence of pulmonary stenosis, which has been reported in approximately 50% of cases. The presence of a VSD causes a systemic-to-pulmonary shunt; however, this is usually balanced because of the protective effect of coexisting pulmonic stenosis.2
Abnormal tricuspid valve morphology with an incidence as high as 90% in autopsy series, but clinically relevant abnormalities are less common and include dysplasia (malformed or imperforate leaflets), apical displacement of the septal leaflet (Ebstein-like malformation), or straddling and overriding of an inlet ventricular septal defect.
Rarely coarctation and interrupted aortic arch have also been frequently reported, but subvalvular and valvular aortic stenosis are quite uncommon.
In general, the coronary arteries follow the morphologic ventricle. A single right coronary artery supplies the systemic right ventricle. The left main, circumflex and left anterior descending artery supply the subpulmonary left ventricle. Anomalies are very common with many patients having a single sinus origin of the 2 main coronaries or from a single stem.
CC-TGA is called “congenitally corrected” TGA because of the normal physiologic movement of blood from the body to the heart to the lungs and back to the heart. In the absence of associated defects, the patients are not cyanotic. It is a misnomer, because these patients are not completely corrected and have lifelong risks of complications from their congenital heart disease.
The term L-TGA is frequently encountered. The L-loop indicates a left (levo) bend in the embryonic heart tube. In a completely formed heart, it refers to the inlet portion of the right ventricle. In L-TGA (CC-TGA) the right ventricle is on the left. In normally looped hearts, including d-transposition of the great arteries (D-TGA) (see Chapter 5 on D-TGA) the right ventricle is on the right (dextro).
Because the morphologic right ventricle is on the left, and the morphologic left ventricle is on the right, this lesion is also sometimes called ventricular inversion.
The most recent adult congenital heart disease (ACHD) guidelines use the term congenitally corrected TGA (CC-TGA). Because this term is used by most recent research publications, it is the term that is used in this chapter.
FIGURE 6-1
A. Normal connections between heart, lungs, and body. B. CCTGA demonstrates the primary abnormality of “ventricular inversion” where the morphologic left ventricle is pumping to the lungs and the morphologic right ventricle is pumping to the body. In the absence of associated anomalies, the patients are not cyanotic.
FIGURE 6-2
A 3D reconstruction of a computed tomography (CT) scan of a waxed heart specimen with CC-TGA and ventricular septal defect. The right-sided right atrium (RA) is aligned with the right-sided left ventricle (LV) via the mitral valve (MV) and the left-sided left atrium with the right ventricle (RV) through the tricuspid valve (TV). The pulmonary artery (PA) is aligned with the LV and there is mitral pulmonary fibrous continuity (white arrow). The aorta (Ao) is aligned with the RV and is separated from the tricuspid valve by subaortic conus (bracket). There is a large ventricular septal defect (*) in this specimen.
Prenatally diagnosed CC-TGA is rare:
In the absence of associated anomalies, it requires high degree of suspicion.
Parallel great vessels are a typical clue.
Heart failure
Infants may present with heart failure if they have significant associated defects.
Older patients may present chronic systemic right ventricular failure. The right ventricle is not structurally well suited for systemic pressures and can fail over time.
Chronic tricuspid (systemic atrioventricular) regurgitation can also lead to heart failure.
Heart block
Patients may present with new-onset fatigue and/or exercise intolerance due to the presence of heart block.
Cyanosis is present if there is a large VSD and either pulmonary stenosis or pulmonary vascular disease. Otherwise, patients are not cyanotic.1
Jugular venous pulsation may give clue to conduction abnormalities:
2:1 block will have twice as many A waves and V waves.
Complete heart block can give rise to cannon A waves when the atria contract against a closed atrioventricular valve.
Palpation may be nearly normal:
Because of the “banana” shape of the right ventricle, the apical impulse may be diffuse.
Closure of the aortic valve may be palpated due to its anterior location.
Thrills may be felt due to a ventricular septal defect or pulmonary stenosis.
Auscultation
The first heart sound may be soft or of varying intensity if there is conduction system disease.
Second heart sound is loud because of its anterior location. Pulmonary component of the second heart sound is soft because of its more posterior location.
Ventricular septal defect murmur is similar to patients without CC-TGA—holosystolic and may be absent if shunt is reversed.
Pulmonary stenosis murmur is softer than degree of obstruction compared to patients without CC-TGA because of the posterior location of the pulmonary valve. It is located at the third left intercostal space and radiates upward and to the right.
Left atrioventricular (tricuspid) valve regurgitation murmur is similar to patients without CC-TGA with mitral regurgitation. It is an apical, holosystolic murmur.
An ECG can provide the most significant clue of this condition with the presence of Q waves over the right precordium due to reverse septal depolarization with absent Q waves over the lateral precordium with lack of other criteria for right ventricular hypertrophy.
Q waves also common in lead III and aVF (inferior myocardial infarction [MI] pattern).
PR interval is frequently prolonged (Figure 6-3). 2:1 block and complete heart block may be present.
P waves typically normal, unless severe tricuspid regurgitation (left atrial enlargement—broad, notched P waves) or pulmonary stenosis (right atrial enlargement—tall, peaked P waves)
Bundle branches are inverted, so septal activation is right to left.
T waves usually upright in V1 to V6.
Often the findings can be subtle.
Vascular pedicle is narrow.
Left-sided heart border has a “humped” appearance.
Severe left-sided atrioventricular (tricuspid) valve regurgitation can lead to cardiomegaly.
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