DESCRIPTION

Corrected transposition of the great arteries, ventricular inversion, or L transposition of the great arteries (L-TGA) is defined as a congenital cardiac malformation in which the systemic venous blood returns to an anatomic right atrium, which is connected to an anatomic LV and then to the pulmonary artery. The pulmonary venous blood returns to an anatomic left atrium, which is connected to the anatomic RV and then to the aorta. This combination of atrioventricular discordance and ventriculoarterial discordance results in a physiologically "corrected" normal circulation.

EPIDEMIOLOGY

This is a relatively uncommon cardiac defect that affects 0.6–0.9% of all patients with congenital heart defects. Only 1% of these patients have no other associated cardiac abnormalities. There is a higher incidence in males (63–76%).

ETIOLOGY

Unknown

COMMONLY ASSOCIATED CONDITIONS

L-TGA can be an isolated anatomic defect without major clinical manifestations. However, this lesion is usually associated with other cardiac malformations such as ventricular septal defect (VSD), pulmonary outflow tract obstruction, abnormalities of the systemic atrioventricular valve (Ebstein-type malformation), and conduction system defects. These patients have a fragile conduction system, and there can be a progressive incidence of developing complete heart block (1–2%/yr). The presence of associated intracardiac malformations is so common that they should be considered as part of the disease.

Outline

• Description
• Epidemiology
• Etiology
• Commonly Associated Conditions

Signs and symptoms:

• The timing of presentation in cases of L-TGA is significantly influenced by the presence of associated malformations. The majority of the patients have signs or symptoms in the 1st few months of life, depending on the predominant associated lesion. The infant may present with signs or symptoms of CHF if the predominant associated lesion is a ventricular septal defect or systemic atrioventricular valve regurgitation, or with cyanosis in the presence of pulmonary outflow tract obstruction with VSD.
• Older patients can present with signs and symptoms of CHF secondary to poor systemic RV function or progressive tricuspid (systemic) atrioventricular valve regurgitation. With balanced anomalies, patients can remain symptom free for years or even decades.
• Some patients are diagnosed during evaluation of a heart murmur or after seeing an abnormal CXR obtained for other reasons.

Physical Exam

• The physical exam findings are determined by the presence of the associated lesions.
• Most patients are acyanotic unless severe pulmonary stenosis with VSD is present.
• A loud single 2nd heart sound is characteristic in patients with L-TGA due to the anterior position of the aortic valve.
• The characteristics of the murmur depend on the predominant associated lesion (ventricular septal defect, pulmonary stenosis, or tricuspid regurgitation).

DIAGNOSTIC TESTS & INTERPRETATION

• EKG usually shows reversed septal depolarization with Q waves that are present in the right precordial leads, but absent over the left precordium (the initial ventricular septal activation is from right to left).
• Ambulatory 24-hr EKG recording (Holter) is periodically used to follow atrioventricular nodal function in this group of patients where progressive atrioventricular block is common.

Imaging

• CXR may show a leftward ascending aorta with a straight border that can be seen at the left upper border of the cardiac silhouette. Similar to the other clinical findings, the radiographic findings depend on the position of the heart and the presence of associated lesions.
• Echo is the optimal method for diagnosis and evaluation of L-TGA and associated lesions. The main finding is the presence of ventricular inversion. The anatomic right atrium connects through a mitral valve (with two papillary muscles) to a morphologic LV with smooth wall located on the right side. The anatomic left atrium connects via a tricuspid valve to a morphologic left-sided RV characterized by chordal attachments of the atrioventricular valve to the septum, coarse trabeculations, and the presence of a moderator band. The systemic AV valve (tricuspid valve) should be assessed. Often there is tricuspid valve regurgitation with Ebstein’s malformation of the valve.
• Cardiac catheterization is not necessary to establish the diagnosis of L-TGA; however, it may be needed to assess the hemodynamic status in certain cases before surgery. Special care should be taken to avoid catheter trauma to the delicate conduction system.
• Echo assessment of the function of a morphologic RV is challenging because of the complex shape of this chamber. In recent years, cardiac MRI has evolved to be a good quantitative standard, especially for serial comparisons.

DIFFERENTIAL DIAGNOSIS

• The differential diagnosis of L-TGA depends on the associated lesions.
• Patients with RV outflow tract obstruction should be differentiated from patients with tetralogy of Fallot or ventricular septal defect with pulmonary stenosis.
• The differential diagnosis in patients with CHF includes ventricular septal defect, endocardial cushion defects, and patent ductus arteriosus.

Outline

• Information
• Physical Exam
• Diagnostic Tests & Interpretation
  • Imaging
• Differential Diagnosis

• In case of significant RV outflow tract obstruction at birth, the newborn requires prostaglandin infusion to maintain ductal patency.
• Patients with large ventricular septal defects, RV failure, or severe tricuspid valve regurgitation need anticongestive treatment and diuretics.
• Endocarditis prophylaxis is not required on a routine basis.

ADDITIONAL TREATMENT

General Measures

• Patients with L-TGA and no associated cardiac defects do not require intervention.
• The nature of the associated cardiac defect will determine the need for intervention. A neonate with severe cyanosis secondary to pulmonary outflow tract obstruction will need surgical palliation by placement of a systemic-to-pulmonary artery shunt. Conversely, an infant with CHF due to a large ventricular septal defect may need anticongestive therapy or even pulmonary banding or surgical closure of the defect.

SURGERY

• Until the recent era, surgery for patients with L-TGA and pulmonary stenosis and ventricular septal defect consisted of closure of the defect and a conduit from the LV to the pulmonary artery. This repair leaves the RV as the systemic pumping chamber.
• A double-switch operation has been considered an attractive surgical alternative for L-TGA and these defects. This procedure combines an atrial switch operation (Senning or Mustard operation) with either an arterial switch operation or, if pulmonary stenosis is present, the Rastelli procedure (tunneling the anatomic LV to the aorta through a ventricular septal defect and placement of a RV-to-pulmonary artery conduit). In this way, the morphologic LV becomes the systemic ventricle and the morphologic RV, the pulmonary ventricle.
• In case of complete heart block, permanent transvenous or epicardial pacemaker is implanted when the patient meets the criteria determined by the American Heart Association (AHA) and American College of Cardiology (ACC).

Outline

• Additional Treatment
  • General Measures
• Surgery

FOLLOW-UP RECOMMENDATIONS

Patient Monitoring

Frequent follow-up is necessary following the state of the tricuspid valve, ventricular function, and cardiac rhythm.

PROGNOSIS

• The natural history of L-TGA is determined by the presence of associated cardiac defects and the onset of acquired changes. Although long life expectancy is possible, it is rare in the unrepaired patient. There is a high incidence of systemic ventricular dysfunction and CHF, leading to high mortality rate, particularly in patients with tricuspid (systemic valve) regurgitation, heart block, or other associated cardiac defects.
• When the RV fails as a systemic ventricle despite anticongestive therapy, cardiac transplantation may be the only alternative.
• The results of pregnancy with L-TGA depend on the status of ventricular function and the presence of associated lesions. Cardiac risks are increased in patients with cyanotic forms of this lesion.

Outline

• Follow-Up Recommendations
  • Patient Monitoring
• Prognosis

CODES

ICD9

745.12 Corrected transposition of great vessels

SNOMED

83799000 corrected transposition of great vessels (disorder)

ADDITIONAL READING

• Bove EL, Ohye RG, Devaney EJ, et al. Anatomy correction of congenitally corrected transposition and its close cousins. Cardiol Young 2006;16(Suppl 3):85–90.
• Epstein AE and writing committee members. ACC/AHA/HRS 2008 guidelines for device based therapy of cardiac rhythm abnormalities: Executive summary. Circulation. 2008;117:2820–2840.
• Freedom RM. Discordant atrioventricular connections and congenitally corrected transposition. In: Anderson RH, Baker EJ, Macartney FJ, et al. Pediatric Cardiology. London: Churchill Livingstone, 2002:1321–1351.
• Lundstrom U, Bull C, Wyse RKH, et al. The natural and "unnatural" history of congenitally corrected transposition. Am J Cardiol. 1990;65:1222–1229.
• Mee RBB. The double switch operation with accent on the Senning component. Semin Thorac Cardiovasc Surg Ped Card Surg Ann 2005;8:57–65.
• Prieto LR, Hordof AJ, Secir M, et al. Progressive tricuspid valve disease in patients with congenitally corrected transposition of the great arteries. Circulation. 1998;98:997–1005.
• Rutledge JM, Nihill MR, Fraser CD, et al. Outcome of 121 patients with congenitally corrected transposition of the great arteries. Pediatr Cardiol. 2002;23:137–145.
• Van Praagh R, Papagiannis J, Gründenfelder J, et al. Pathologic anatomy of corrected transposition of the great arteries: Medical and surgical implications. Am Heart J. 1998;135:772–785.

Leonardo Liberman

Welton M. Gersony