Congenitally Corrected Transposition of the Great Arteries (ccTGA)

Congenitally corrected transposition of the great arteries (ccTGA) is characterized by abnormal connections between the atrium, ventricles and great arteries (atrioventricular and ventriculoarterial discordance).

In ccTGA the ventricles are L looped. This means there is abnormal leftward looping of the primitive heart, which results in abnormal positioning of the ventricles. Instead of their typical locations, the morphologic right ventricle is now located on the left side and the morphologic left ventricle on the right side.

Atrioventricular discordance refers to an abnormal connection between the atria and ventricles. The tricuspid and mitral valves go with their corresponding ventricles. In ccTGA, the morphologic right atrium is connected to the morphologic right sided left ventricle (right atrium à mitral valve à left ventricle) and the morphologic left atrium is connected to the morphologic left sided right ventricle (left atrium à tricuspid valve à right ventricle).

Ventriculoarterial discordance is defined as the pulmonary artery (right sided great artery) being connected to the right sided morphologic left ventricle (left ventricle à pulmonary artery), and the aorta (left sided great artery) being connected to the left sided morphologic right ventricle (right ventricle à aorta). Because there are discordant connections at both levels, the circulation of blood flow remains hemodynamically correct.

The great arteries are described as L looped. The aorta is positioned anterior and leftward to the pulmonary artery with a well-developed infundibulum below the aortic valve. The infundibulum creates tricuspid and aortic discontinuity.  The spatial relationship between the great arteries and tricuspid/aortic discontinuity help provide supportive findings when diagnosing ccTGA.

The segments for Congenitally Corrected Transposition of the Great Arteries are {S, L, L}:

  • Atrial situs solitus  (S)

  • L looped ventricles (L)

  • L looped great arteries (L)

Utilizing the segmental approach is essential with this rare and complex condition.  In particular, determining the atrial situs, ventricular situs, and great artery arrangement will assist in accurately diagnosing ccTGA.

Associated defects:

  • Ebstein’s anomaly

  • Ventricular septal defect

  • Left ventricular outflow tract obstruction (sub-pulmonic and/or pulmonary stenosis)

  • Right ventricular outflow tract obstruction (sub-aortic and/or aortic stenosis)

 

Optimal Echo Views and findings from those views:

Parasternal long axis:

  • Parallel arrangement of the great arteries.

  • The left ventricle is often difficult to visualize due the side by side positioning of the ventricles.

Parasternal short axis:

  • The aorta is anterior and leftward to the pulmonary artery.

  • The interventricular septum runs parallel (straight anteroposterior plane) with side by side ventricles.

  • The right ventricle positioned leftward to the left ventricle.

Apical and Subcostal:

Determining ventricular morphology (key findings):

  • Positioning of the AV valves

  • Right AV valves septo-phobic (mitral) 

  • Left AV valve septo-phyllic (tricuspid) and more apically displaced

  • Smooth-walled right sided left ventricle 

  • Trabeculated left sided right ventricle

 

  • Properties of a Right Ventricle

    • Trabeculated endocardial surface

    • Presence of moderator band

    • Elliptical shape of the ventricular cavity

    • Tricuspid valve

      • Trileaflet valve that lies closer to the apex than the MV

      • Septo-phyllic (chordal attachments to ventricular septum present)

  • Properties of a Left Ventricle

    • Smooth endocardial surface

    • Mitral valve

      • Chordal attachments are septo-phobic (no attachments to interventricular septum)

 

Suprasternal notch:

A right aortic arch can occur in ~18% of ccTGA

 

 

References:

Earing, M.G., Ayres, N.A., & Cetta, F. (2010). Congenitally Corrected Transposition of the Great Arteries, Echocardiography in Pediatric and Adult Congenital Heart Disease (pp. 145-156). Philadelphia, PA: Lippincott Williams & Wilkins.

Snider, A.R., Serwer, G.A., & Ritter, S.B. (1997). Abnormalities of Ventriculoarterial Connection, Echocardiography in Pediatric Heart Disease. 2nd ed. (pp. 317-323). St. Louis, MO: Mosby-Year Book, Inc.