TRANSPOSITION OF THE GREAT VESSELS

Two types:

  1. Complete or dextro-transposition (D-TGA) (80%).
    • Atrioventricular concordance with ventriculo-arterial discordance.
    • Three types are described:
      • TGA with intact ventricular septum with / without pulmonary stenosis.
      • TGA with VSD.
      • TGA with VSD and pulmonary stenosis.
    • Associated anomalies especially cardiac (pulmonary stenosis) occur.
    • Aorta arises from RV receives systemic blood and returns it to the systemic system. The pulmonary artery receives pulmonary venous blood, and returns it to the lungs. The aortic root lies anterior and slightly to the right of the pulmonary outflow tract. This is incompatible with life with closure of the ductus and foramen ovale after birth.
  2. Congenitally corrected or levo-transposition (L-TGA) (20%).
    • Atrioventricular discordance with ventriculo-arterial discordance.
    • The aorta arises from the RV is anterior and to the left of the pulmonary artery.
    • VSD and pulmonary stenosis occur in 50% of cases.
    • Malformation and inferior displacement of the tricuspid valve may occur.

 

ULTRASOUND

 

 

 

Complete TGV (d-TGV)

Congenitally corrected TGV (ccTGA)

Great vessels enter the heart in parallel rather than crossing each other. On the short axis view the aorta and pulmonary artery are both circular structures adjacent to each other (normally the pulmonary artery wraps around the circular aorta. Differentiation of the two types involves identification of the morphologic right and left ventricles.

Embryology

 

Abnormal left-looping (l-ventricular looping)

Morphologic RV becomes left sided

Morphologic LV becomes right sided

IVS more horizontal due to relative supero-inferior positioning of ventricles

Conotruncal septum does not rotate resulting in the parallel arrangement of outflow tracts

Atrio-ventricular arrangement

Concordance

Discordance

Ventriculo – arterial arrangement

Discordance

Discordance

Systemic veins

Drain into RA

Drain into morphologic RA

Pulmonary artery

 

Transposed. Arises from morphological LV

Aorta

Lies to right and anterior to PA

Transposed. Arises from RV. Located anteriorly and to left of pulmonary trunk

Pulmonary veins

Drain into LA

Drain into LA

Right atrium

 

Connected to morphological LV by mitral valve

Left atrium

 

Connected to morphological RV by tricuspid valve

Inter-atrial septum

 

May be malaligned relative to IVS

Right ventricle

 

Morphological RV lies posterior and to left of morphologic LV

Associated Anomalies

 

Cardiac malpositioning

Situs inversus

Tricuspid valve dysplasia / atresia

Double outlet ventricle

VSD (about 50%) – usually large and perimembranous

Predisposes to congenital heart block

Presentation

 

In the absence of associated anomalies patients may be asymptomatic with presentation not uncommon in adult life.

Antenatal ultrasound

Parallel great vessels

 

Parallel great vessels

Important to distinguish and differentiate morphologic LV and RV

 

 

 

Right ventricle

Prominent moderator band.

More apical attachment of atrio-ventricular valve.

Chordal attachment of AV valve directly to septum.

Irregular endocardial surface

Cavity has a more rounded or triangular shape

Papillary muscles attach distally and centrally.

No moderator band

 

 

 

 

Smooth endocardial surface

Cavity has a more elongated shape

 

Papillary muscles attach to sidewall of ventricle

d-TGV

cc-TGV

 

cc-TGA – morphological RV attached to LA and morphological LV attached to RA

 

 

d-TGV

 

Case 1

Case 2

Left atrium (LA) connected to morphological left ventricle (LV)

Right atrium (RA) connected to morphological right ventricle

Large VSD

Main pulmonary artery (MPA) arising from LV

Aorta arising from right ventricle

 

 

cc-TGV

4 chamber view – morphological LV (papillary muscles attach to sidewall + mitral valve) connects to RA.

                            - morphological RV(moderator band, papillary muscles attach to apex, and tricuspid valve) connects to LA.

Parallel outflow tracts (PA from LV and aorta from RV).

Pulmonary artery bifurcation – note the abnormal arrangement of the vessels with the PA situated between the aorta and SVC.

 

 

 

 

 

 

 

 

 

d-TGV – gray scale

d-TGV – sagittal color flow

 

 

 

 

 

CONDITIONS AND SYNDROMES ASSOCIATED WITH D- AND L- TGA

 

Link to Conditions and Syndromes Associated with D- and L- TGA