Transposition of the great arteries (D-TGA) is a conotruncal abnormality characterized by discordant ventricular-arterial connections. In D-TGA, the aorta arises from the right ventricle and the pulmonary artery arises from the left ventricle. The aorta is anterior and rightward. The pulmonary and aortic circulations are in parallel instead of in series.
D-TGA occurs in ~31.5 in 100,000 live births
D-TGA is the second most common cyanotic heart disease following tetralogy of Fallot
Male predominance (2:1 male to female ratio)
Rarely hereditary, however, infants of diabetic mothers are at increased risk.
Ventricular septum: Intact (60%) vs ventricular septal defect (VSD) (40%).
Pulmonary stenosis (30%).
TGA/VSD can be associated with overriding or straddling AV valves
Hypoplastic aortic arch/coarctation of aorta.
Outflow tract obstruction (most commonly left ventricular outflow tract)
D-TGA can be missed as the apical 4 chamber view often appears normal with symmetric ventricles and normal appearing AV valves
On outflow tract sweeps, the great arteries DO NOT CROSS, rather they are in parallel with the aorta anterior and rightward to the pulmonary artery
Five chamber view demonstrates the pulmonary artery (early bifurcating vessel into two branches, right and left pulmonary arteries) arising from the posterior left ventricle
On longitudinal views, the aortic arch is seen arising from the anterior right ventricle and giving rise to the head and neck vessels
Establish origin and position of the great arteries from multiple views with good full sweeps to assess great artery relationship to the ventricles
Three-vessel trachea view in most cases will demonstrate a single large vessel (aorta) with the superior vena cava rightward
Short axis view of great arteries demonstrates aorta and pulmonary artery as circular structures next to one another
Assess PFO size and shunting pattern (aneurysmal atrial septum with to-fro motion and bidirectional shunting may indicate a restrictive atrial communication)
Assess PDA and direction of shunting (bidirectional or left-to-right shunting at PDA may indicate restrictive atrial communication)
Multiple sweeps of the ventricular septum to assess for VSDs
Assess right and left ventricular outflow tracts for malalignment/stenosis
Should there be a sizable VSD, assess for LVOT (subpulmonary) stenosis and pulmonary stenosis which are known associations (most often a perimembranous VSD)
Assess pulmonary and aortic valve size and function
Assess aortic arch dimensions and for evidence of hypoplasia/ coarctation
Assess ventricular size and function
Assess atrial communication, ductal shunting and outflow tracts, valvar regurgitation, aortic arch if concern for hypoplasia/coarctation. If VSD, assess size of VSD and outflow tracts and pulmonary/aortic valves for evidence of hypoplasia/stenosis
Depends on whether concerns for coarctation, pulmonary stenosis or restrictive atrial septum. PGE can assist in mixing postnatally so may be started until postnatal anatomy (atrial communication, aortic arch assessment) can be fully defined
If there are concerns for a restrictive atrial communication, arrangements with the interventional cath team are critical
Restrictive atrial septum may cause cyanosis and hemodynamic instability postnatally
Urgent balloon atrial septostomy may be required to aid in mixing
Moodie. 2014. Clinical management of congenital heart disease from infancy to adulthood.
Cohen. 2016. Multimodality Imaging Guidelines of Patients with Transposition of the Great Arteries: A Report from the American Society of Echocardiography Developed in Collaboration with the Society for Cardiovascular Magnetic Resonance and the Society of Cardiovascular Computed Tomography. J Am Soc Echocardiogr. 2016 Jul;29(7):571-621.
Abuhamad A, Chaoui R. A Practical Guide to Fetal Echocardiography: Normal and Abnormal Hearts. 2nd Edition. 2009.