Congenitally corrected transposition of the great arteries

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. In this condition, the aorta arises from the morphologic right ventricle, and the pulmonary artery arises from the morphologic left ventricle. However, the atria are also connected to the opposite ventricles (atrioventricular discordance), so blood still flows in the correct physiological direction — deoxygenated blood reaches the lungs and oxygenated blood reaches the body. This double discordance is why the condition is described as 'congenitally corrected.' Despite the physiologically corrected circulation, ccTGA is associated with significant long-term complications. The morphologic right ventricle must function as the systemic ventricle, pumping blood against systemic pressures, a role for which it is not ideally suited. Over time, this can lead to systemic ventricular dysfunction and heart failure. The tricuspid valve, which serves as the systemic atrioventricular valve in ccTGA, is prone to progressive regurgitation. Conduction system abnormalities are common, with a significant proportion of patients developing complete heart block either spontaneously or after surgical intervention. Approximately 60–90% of patients with ccTGA have associated cardiac anomalies, most commonly ventricular septal defect (VSD), pulmonary stenosis or subpulmonary obstruction, and Ebstein-like malformation of the tricuspid valve. Some patients with isolated ccTGA (without associated defects) may remain asymptomatic for decades and may not be diagnosed until adulthood, when symptoms of heart failure, arrhythmias, or exercise intolerance develop. Treatment depends on the associated anomalies and the degree of systemic ventricular dysfunction. Surgical options include conventional repair (addressing associated defects while leaving the morphologic right ventricle as the systemic ventricle) or anatomic repair procedures such as the double switch operation, which restores the morphologic left ventricle to the systemic circulation. Pacemaker implantation may be required for heart block. Heart transplantation may be considered in cases of severe, refractory heart failure. Lifelong cardiology follow-up is essential for all patients with ccTGA.

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