Congenitally Corrected Transposition of the Great Arteries

In the more common transposition of the great arteries (dextro-transposition or d-TGA), the aorta arises directly from the right ventricle and the pulmonary artery arises from the left ventricle, resulting in independent, parallel pulmonary and systemic circulations; oxygenated blood cannot reach the body except through openings connecting the right and left sides (eg, patent foramen ovale, atrial or ventricular septal defects). This type of transposition results in immediate postnatal severe cyanosis and requires immediate intervention at birth and surgical correction within the first week of life.

In congenitally corrected transposition (levo-transposition [l-TGA] CCTGA), the right atrium connects to a right-sided morphologic left ventricle (LV) and the left atrium connects to a left-sided morphologic right ventricle (RV). In almost all cases, the morphologic LV connects to the pulmonary artery and the morphologic RV connects to the aorta. The circulation is thus physiologically “corrected,” but clinical symptoms and adverse hemodynamic sequelae are almost always present. These sequelae result from the anomalies that frequently are associated with CCTGA or from having a morphologic right ventricle supporting the systemic circulation. The vast majority of patients with CCTGA have one or more of the following associated defects (1, 2):

• VSD (> 60%)

• Pulmonic stenosis (40%)

• Ebstein anomaly or other dysplasia of the left sided tricuspid valve (90%)

• Congenital or acquired AV block (progressive in 2% per year, 10 to 15% by adolescents and up to 30% in adults)

• Malposition with mesocardia or dextrocardia (20%)

• Progressive dysfunction of the systemic right ventricle (50% by 30 years of age)

There is a wide range of clinical manifestations due to the multiple associated anomalies.

During infancy, CCTGA may present with a murmur due to pulmonary stenosis or a VSD, cyanosis due to severe pulmonic stenosis and a VSD, heart failure due to a large VSD, or symptomatic bradycardia due to congenital complete AV block. These symptoms may develop gradually during childhood and adolescence depending on the severity of the associated lesions.

As patients reach adulthood, a common concern is the development of dysfunction of the morphologic RV, which serves as the systemic ventricle. This dysfunction may be subclinical or manifest as a severe cardiomyopathy and heart failure. Because of the anatomic abnormalities almost universally present in the left-sided tricuspid valve, progressive tricuspid regurgitation is common and exacerbates the tendency for heart failure.

• Physical examination

• Chest x-ray and ECG

• Echocardiography

• MRI and CT

• Cardiac catheterization

Clinical findings will depend on the associated lesions, but a universal finding is the presence of a loud single second heart sound (S2) heard at the base of the heart due to the leftward and anterior location of the aorta. The aortic closure sound often generates a localized palpable impulse at the upper right or left parasternal area.

The ECG may show AV block or abnormal Q waves in the right precordial leads (due to reversal of septal depolarization). There is an increased incidence of Wolff-Parkinson-White (WPW) syndrome with this anomaly.

The chest x-ray usually shows a straight upper left heart border (because of the abnormal position of the ascending aorta) in addition to a more midline or right-sided position of the heart.

The diagnosis should be obvious on the echocardiogram, which demonstrates the morphology of the ventricles to be reversed with the right-sided ventricle (morphologic LV) giving rise to a posterior pulmonary root and left-sided ventricle (morphologic RV) giving rise to an anterior and leftward aortic root. Associated defects are also well defined by this imaging modality.

MRI and CT scans are often used to provide additional anatomic detail and provide the most reliable evaluation of right and left ventricular function.

Cardiac catheterization is sometimes required to accurately evaluate intracardiac pressures, including pulmonary artery pressure and resistance.

• Medications

• Surgery

• Rhythm devices

Medications may be needed for patients with pressure or volume overload or ventricular dysfunction resulting in congestive heart failure.

Surgical treatment is often necessary to repair associated defects such as ventricular defects, pulmonary outflow tract obstruction or tricuspid regurgitation.

Because of the inevitability of progressive cardiac dysfunction in the adult years, many clinicians consider the "double switch" as a surgical option in childhood. This procedure involves switching the aorta and pulmonary arteries to the morphologically appropriate ventricles and switching the venous return with an intraatrial baffle, which directs vena caval return to the left-sided RV and the pulmonary venous return to the right-sided left ventricle. This complex procedure eliminates the inherent disadvantage of the CCTGA circulation, namely having a morphologic RV to supply the systemic circulation.

Pacemakers are generally required if patients have AV block, and adults with moderate to severe RV dysfunction and risk for ventricular arrhythmias may receive implantable cardioverter defibrillators.

Patients with severe manifestations, including progressive cardiomyopathy due to RV dysfunction, may require heart transplantation.

• In congenitally corrected transposition of the great arteries, the right atrium enters a right-sided morphologic left ventricle, which gives rise to the pulmonary artery, and the left atrium connects to a left-sided morphologic right ventricle, which then leads to the aorta.

• There is a wide range of clinical manifestations due to the multiple associated anomalies.

• As patients reach adulthood, a concern is the development of dysfunction of the morphologic RV, which serves as the systemic ventricle.

• The diagnosis is usually made via echocardiogram, which demonstrates the morphology of the ventricles to be reversed with the right-sided morphologic left ventricle giving rise to a posterior pulmonary root and left-sided morphologic right ventricle giving rise to an anterior and leftward aortic root.

• Treatment is with a combination of medical, surgical, and rhythm device modalities.

The following English-language resources may be useful. Please note that THE MANUAL is not responsible for the content of these resources.

1. American Heart Association: Common Heart Defects: Provides overview of common congenital heart defects for parents and caregivers

2. American Heart Association: Infective Endocarditis: Provides an overview of infective endocarditis, including summarizing prophylactic antibiotic use, for patients and caregivers