Transposition of the great arteries
Transposition of the great arteries (TGA) is the most common cyanotic congenital cardiac anomaly with cyanosis in the first 24 hours of life. It accounts for up to 7% of all congenital cardiac anomalies 1 and can be assessed with echocardiography, gated cardiac CT, or cardiac MRI.
The estimated incidence is at ~1 in 5000 births. Transposition of the great arteries is an isolated abnormality in 90% of those affected and rarely is associated with a syndrome or an extra-cardiac malformation. It is most common in infants of diabetic mothers 1.
Occurs as a result of ventriculoarterial discordance, with the aorta arising from the right ventricle and the pulmonary trunk from the left ventricle. It can be subdivided into two main types depending on the positional relationship of the aortic valve with the pulmonary valve:
- L-loop transposition of the great arteries: congenitally corrected TGA
- D-loop transposition of the great arteries
This article mainly focuses on the D-loop transposition.
An isolated TGA is incompatible with life at birth without one of the following additional anomalies (which are a common occurrence 2):
- atrial septal defect (ASD): uncommon
- ventricular septal defect (VSD): ~35%
- patent ductus arteriosus (PDA): unstable due closure following birth
- patent foramen ovale (PFO): unstable
Unstable associations account for 60-65% of occurrences.
Approximately 90% of TGAs occur as an isolated finding, and extracardiac syndromic associations are rare. Associations have been described with:
- maternal diabetes
- congenital coronary arterial anomalies
A frontal chest radiograph classically shows cardiomegaly with cardiac contours classically described as appearing like an egg on string 1. There is often an apparent narrowing of the superior mediastinum as the result of the aortic and pulmonary arterial configuration, i.e. parallel in D-loop transposition, with the main pulmonary artery posterior to the aorta.
Allows direct visualisation of abnormal anatomy with the aorta and pulmonary trunk lying in parallel with an absence of crossing (best seen in the base view of the fetal heart) 4.
Allows direct visualisation of abnormal great vessel anatomy. Cardiac-gated cine CT can additionally assess function.
Allows direct visualisation of abnormal anatomy. SSFP cine sequences can additionally determine flow dynamics.
Treatment and prognosis
Initial Rashkind septoplasty is usually done as a palliative procedure in neonates.
Definitive surgical correction
Congenital heart disease
There is more than one way to present the variety of congenital heart diseases. Whichever way they are categorised, it is helpful to have a working understanding of normal and fetal circulation, as well as an understanding of the segmental approach to imaging in congenital heart disease.
congenital heart disease
- normal relationship between chambers and valves
- atrioventricular valves
- outflow tract
- great vessels
- venous inflow
- anomalous valves
- abnormal relationship of chambers and valves
- atrioventricular abnormality
- great vessel connection abnormality
- conotruncal cardiac anomalies
- pentalogy of Cantrell
- Shone syndrome
- congenital heart disease - chest x-ray approach
surgical repairs (mnemonic)
- arterial switch procedure
- Blalock-Taussig shunt
- double switch procedure
- Fontan procedure
- Glenn procedure
- Mustard repair
- Norwood procedure
- Pott shunt
- pulmonary artery banding
- Rastelli procedure
- Sano shunt
- Senning repair
- total repair of tetralogy of Fallot (TOF)
- unifocalisation procedure
- Waterston shunt
- acute aortic syndrome
- thoracic aortic aneurysm
- abdominal aortic aneurysm
- endovascular aneurysm repair (EVAR)
- reporting tips for aortic aneurysms
- aortic coarctation
- aortic pseudocoarctation
- cervical aortic arch
- interrupted aortic arch
- transposition of the great arteries
- variant anatomy of the aortic arch
- traumatic aortic injuries
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- 2. Reddy GP, Caputo GR. Diagnosis please. Case 15: congenitally corrected transposition of the great arteries. Radiology. 1999;213 (1): 102-6. Radiology (full text) - Pubmed citation
- 3. Donnelly LF, Higgins CB. MR imaging of conotruncal abnormalities. AJR Am J Roentgenol. 1996;166 (4): 925-8. AJR Am J Roentgenol (abstract) - Pubmed citation
- 4. Barboza JM, Dajani NK, Glenn LG et-al. Prenatal diagnosis of congenital cardiac anomalies: a practical approach using two basic views. Radiographics. 22 (5): 1125-37. Radiographics (full text) - Pubmed citation
- 5. Moss AJ, Allen HD, Driscoll DJ et-al. Moss and Adams' heart disease in infants, children, and adolescents, including the fetus and young adult. Lippincott Williams & Wilkins. (2007) ISBN:0781786843. Read it at Google Books - Find it at Amazon
- 6. Entezami M, Albig M, Knoll U et-al. Ultrasound Diagnosis of Fetal Anomalies. Thieme. (2003) ISBN:1588902129. Read it at Google Books - Find it at Amazon