Congenitally uncorrected transposition of the great arteries (congenitally uncorrected TGA), also referred to as complete transposition, is a congenital cardiac malformation characterized by atrioventricular concordance and ventriculoarterial (VA) discordance.
The incidence is estimated at 1 in 3,500-5,000 live births, with a male-to-female ratio of 1.5 to 3.2:1.
In 50% of cases, the VA discordance is an isolated finding. In 10% of cases, TGA is associated with noncardiac malformations. The association with other cardiac malformations such as ventricular septal defect (VSD) and left ventricular outflow tract obstruction is frequent and dictates the timing and clinical presentation, which consists of cyanosis with or without congestive heart failure. The onset and severity depend on anatomical and functional variants that influence the degree of mixing between the two circulatory systems. If no obstructive lesions are present and there is a large VSD, cyanosis may go undetected and only be perceived during episodes of crying or agitation. In these cases, signs of congestive heart failure prevail.
The exact etiology remains unknown. Some associated risk factors (gestational diabetes mellitus, maternal exposure to rodenticides and herbicides, and maternal use of antiepileptic drugs) have been proposed. Mutations in the growth differentiation factor-1 gene (GDF1), the mediator complex subunit 13-like gene (MED13L) and the gene encoding the cryptic protein (CFC1) have been shown to be implicated in discordant VA connections, but they account for only a small minority of congenitally uncorrected TGA cases.
The diagnosis is confirmed by echocardiography, which also provides information about the morphological details required for future surgical management.
The differential diagnosis should include other causes of central neonatal cyanosis.
Prenatal diagnosis by fetal echocardiography is feasible and useful as it may improve early neonatal management and reduce morbidity and mortality.
Palliative treatment with prostaglandin E1 and balloon atrial septostomy are usually required soon after birth. Surgical correction is performed at a later stage. Usually, the Jatene arterial switch operation is the procedure of choice. Whenever this operation is not feasible, an adequate alternative surgical approach should be implemented.
With the advent of newer and improved surgical techniques and improved post-operative intensive care, the long-term survival is approximately 90% at 15 years of age. However, exercise performance, cognitive function and quality of life may be impaired.
Last update: October 2008
- Dr Eduardo CASTELA
- Dr Paula MARTINS