Isolated congenitally uncorrected transposition of the great arteries

Isolated congenitally corrected transposition of the great arteries (ccTGA), also known as L-transposition of the great arteries or ventricular inversion, is a rare congenital heart defect in which the heart's two lower chambers (ventricles) are reversed from their normal positions. In this condition, the aorta arises from the morphologic right ventricle (which is positioned on the left side), and the pulmonary artery arises from the morphologic left ventricle (positioned on the right side). The atrial-ventricular connections are also discordant, meaning that deoxygenated blood from the right atrium flows into the morphologic left ventricle and then to the lungs, while oxygenated blood from the left atrium flows into the morphologic right ventricle and then to the body. Because of this double discordance, blood flow is physiologically corrected — oxygenated blood still reaches the body — hence the term 'congenitally corrected.' The 'isolated' designation (Orphanet code 216718) refers to cases occurring without additional associated cardiac malformations such as ventricular septal defect, pulmonary stenosis, or tricuspid valve abnormalities. Despite the physiologic correction of blood flow, the morphologic right ventricle must support the systemic circulation, a role for which it is not ideally designed. Over time, this can lead to progressive systemic (morphologic right) ventricular dysfunction, systemic atrioventricular (tricuspid) valve regurgitation, heart failure, and conduction system abnormalities including complete heart block. Many patients with isolated ccTGA may remain asymptomatic for years or even decades, with some not being diagnosed until adulthood. Symptoms, when they develop, may include exercise intolerance, fatigue, palpitations, and signs of heart failure such as shortness of breath and fluid retention. Management of isolated ccTGA depends on the clinical course and the development of complications. Regular cardiac monitoring with echocardiography and assessment of ventricular function is essential. Medical therapy for heart failure may be employed when systemic ventricular dysfunction develops. Pacemaker implantation may be necessary for patients who develop significant heart block. In select cases with severe systemic ventricular failure, surgical options including the double switch operation (anatomic repair) or cardiac transplantation may be considered. Early diagnosis and long-term follow-up by specialists in congenital heart disease are critical for optimizing outcomes.

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