Tuesday, February 7, 2023

Transposition of the Great Arteries

Background

Transposition of the great arteries (TGA) is the most common cyanotic congenital heart lesion that presents in neonates. The hallmark of transposition of the great arteries is ventriculoarterial discordance, in which the aorta arises from the morphologic right ventricle and the pulmonary artery arises from the morphologic left ventricle. See the image below.

This right ventricular angiogram shows a patient w

This right ventricular angiogram shows a patient with transposition of the great arteries. The aorta arises directly from the right-sided anterior right ventricle (10° left anterior oblique [LAO]).

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Although transposition of the great arteries was first described over 2 centuries ago, no treatment was available until the middle of the 20th century, with the development of surgical atrial septectomy in the 1950s and balloon atrial septostomy in the 1960s. These palliative therapies were followed by physiological procedures (atrial switch operation) and anatomic repair (arterial switch operation) (see the videos below). Today, the survival rate for infants with transposition of the great arteries is greater than 90%.

This video shows the repair of a newborn with transposition of the great arteries and ventricular septal defect (VSD) by means of arterial switch and VSD closure. Procedure performed by Giles Peek MD, FRCS, CTh, FFICM, The Children’s Hospital at Montefiore, Bronx, NY. Video courtesy of Montefiore.

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Switch ventricular septal defect (VSD hypoplastic right arch). Procedure performed by Giles Peek MD, FRCS, CTh, FFICM, The Children’s Hospital at Montefiore, Bronx, NY. Video courtesy of Montefiore.

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The major anatomic classifications of transposition of the great arteries depend on the relationship of the great arteries to each other and/or the infundibular morphology. In approximately 60% of the patients, the aorta is anterior and to the right of the pulmonary artery (dextro-transposition of the great arteries [d-TGA]). However in a subset of patients, the aorta may be anterior and to the left of the pulmonary artery (levo-transposition of the great arteries [l-TGA]). In addition, most patients with transposition of the great arteries (regardless of the spacial orientation of the great arteries) have a subaortic infundibulum, an absence of subpulmonary infundibulum, and fibrous continuity between the mitral valve and the pulmonary valve. Despite these useful classifications, several exceptions are noted, and, hence, discordant ventriculoarterial connection is the only distinguishing characteristic that defines transposition of the great arteries.

From a practical standpoint, the presence or absence of associated cardiac anomalies defines the clinical presentation and surgical management of a patient with transposition of the great arteries. The primary anatomic subtypes are (1) transposition of the great arteries with intact ventricular septum, (2) transposition of the great arteries with ventricular septal defect, (3) transposition of the great arteries with ventricular septal defect and left ventricular outflow tract obstruction, and (4) transposition of the great arteries with ventricular septal defect and pulmonary vascular obstructive disease.

In approximately one third of patients with transposition of the great arteries, the coronary artery anatomy is abnormal, with a left circumflex coronary arising from the right coronary artery (22%), a single right coronary artery (9.5%), a single left coronary artery (3%), or inverted origin of the coronary arteries (3%) representing the most common variants.

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