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Ultrasound Obstet Gynecol 2004; 23: 68–72
Published online 27 November 2003 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/uog.896
Congenitally corrected transposition of the great arteries:
clues for prenatal diagnosis
R. L. McEWING and R. CHAOUI
Department of Obstetrics and Gynecology, Fetal Medicine Unit, Charité Hospital, CCM, Humboldt University, Berlin, Germany
K E Y W O R D S: atrioventricular discordance; corrected transposition; fetal echocardiography
ABSTRACT
Congenitally corrected transposition of the great arteries
(ccTGA) is an uncommon cardiac defect characterized
by the atria connecting with the anatomically discordant
ventricles and the ventricles connecting with discordant
and transposed great arteries. Parallel vessels are evident
in corrected TGA, but as this sign is also present
in complete TGA, a heart anomaly requiring major
cardiac surgery in the postnatal period, it is important
to differentiate between the entities prenatally. Most
cases of ccTGA have associated anomalies but isolated
forms or those with a mild associated cardiac anomaly
are infrequently detected prenatally. We report on three
cases detected between 21 and 25 weeks’ gestation on
screening ultrasound with associated mild findings. One
fetus had an isolated ventricular septal defect (VSD) first
detected at 34 weeks. The child developed heart block
at 4 years of age. The second case was associated with
a small VSD, a tiny pulmonary trunk and a persistent
right umbilical vein. After birth, mild pulmonary stenosis
was found as an additional cardiac finding at 4 months
of age. The third fetus had no additional cardiac
anomalies prenatally, but after birth a bicuspid aortic
valve was detected. The first case needed pacemaker
implantation but the other two children required no
cardiac surgery. Two of the cases were referred because
abnormal vessel anatomy was detected on screening
ultrasound. As prenatal detection of TGA is becoming
a more frequent occurrence, this paper aims to present
clues aiding in the prenatal diagnosis of atrioventricular
and ventriculoarterial discordance, especially in its
differentiation from complete transposition. These details
are crucial for counseling and perinatal management.
Copyright  2003 ISUOG. Published by John Wiley
& Sons, Ltd.
INTRODUCTION
Congenitally corrected transposition of the great arteries
(ccTGA) is an uncommon congenital cardiac anomaly,
accounting for less than 1% of live births with congenital
heart disease. It is characterized by normal veno-atrial
connections, but with discordant atrioventricular and
ventriculoarterial connections, allowing hemodynamic
compensation (Figure 1). Isolated cases and those with
mild anomalies are rarely detected in the neonate.
There are generally associated cardiac anomalies that
influence the prognosis. Parallel vessels are evident in
ccTGA, but as this sign is also present in the more
common complete TGA (d-TGA) (Figure 1), a heart
anomaly requiring major cardiac surgery in the neonatal
period, it is important to differentiate between the
entities prenatally. Careful examination of the ventricles
allows the morphological right and left ventricles to
be distinguished and atrioventricular discordance to
be detected (Figures 2–5). We describe the prenatal
sonographic characteristics and neonatal course of three
cases of essentially isolated corrected transposition.
CASE REPORTS
Case 1
A 31-year-old woman was referred at 25 weeks’ gestation due to inadequate visualization of the four-chamber
heart at another institution. Detailed scanning demonstrated normal growth, no anomalies and a normal
four-chamber view; however, the great vessels were inadequately evaluated. The patient returned 2 weeks later,
at 27 weeks’ gestation, for targeted fetal echocardiography. Two-dimensional (2D) and color Doppler ultrasound
revealed normal abdominal and thoracic situs, but atrioventricular discordance in the four-chamber view. The
anatomic right atrium connected to a right-sided morphologic left ventricle, and the left atrium connected to a
left-sided morphologic right ventricle. Ventriculoarterial
discordance (with levo-transposition) of the great vessels
was evident with the pulmonary trunk arising from the
morphologic left ventricle (situated on the right side) and
Correspondence to: Prof. R. Chaoui, Department of Obstetrics and Gynecology, Charité Medical School, Humboldt University,
Schumannstrasse 20/21, D-10098 Berlin, Germany (e-mail: [email protected])
Accepted: 20 August 2003
Copyright  2003 ISUOG. Published by John Wiley & Sons, Ltd.
CASE REPORT
Prenatal diagnosis of corrected transposition
SVC
69
TP
Ao
LA
RA
TP
Ao
LA
RA
RV
RV
LV
LV
IVC
Complete transposition
(d-TGA)
Corrected transposition
Figure 1 Schemes comparing complete and corrected transposition
of the great arteries. In complete transposition the ventricles are
normally connected (RA with RV, LA with LV), whereas in
corrected transposition there are discordant connections (RA with
LV, LA with RV). Note that the right-sided ventricle has a left
morphology without trabeculation and reaches the heart apex. In
both cases vessels are arising from the ‘wrong’ ventricle and have a
parallel course. In complete TGA the aorta lies to the right of the
pulmonary trunk (d-looping), and in the corrected form to the left
(l-looping). In complete TGA in postnatal life, deoxygenated blood
arriving in the right atrium will enter the right ventricle and thence
the aorta without passing through the lung (causing cyanosis). In
corrected TGA, blood entering the anatomical left ventricle and
then the pulmonary trunk is oxygenated (therefore ‘congenitally
corrected’). RA, LA, right and left atria; RV, LV, right and left
ventricles; Ao, aorta; TP, pulmonary trunk; IVC, SVC, inferior and
superior venae cavae.
the aorta arising from the morphologic right ventricle (situated on the left side). The vessels had a parallel course,
with the aorta lying ventrally and to the left of the pulmonary trunk (l-transposition). There were no additional
anomalies or arrhythmia. The diagnosis of isolated ccTGA
was made. The patient declined karyotyping. A scan at
32 weeks confirmed these findings, and color Doppler
aided in additional identification of a muscular ventricular septal defect (VSD) by showing bidirectional shunting.
Later sonograms showed intrauterine growth restriction
with normal fetal Doppler indices and normal cardiac
rhythm. A male infant weighing 2890 g was delivered
spontaneously at 38 weeks’ gestation at our center. Postnatal echocardiography confirmed the prenatal findings.
The newborn was discharged at 6 days of age. By age
12 months, echocardiography demonstrated spontaneous
closure of the VSD. Later echocardiographic examinations showed normal ventricular contractility until 4 years
of age when intermittent bradycardia became apparent.
Twenty-four hour electrocardiogram (ECG) monitoring
revealed an intermittent atrioventricular block with a ventricular rate of 55 bpm, necessitating pacemaker insertion
at 5 years of age. The child remains well at 6 years of age,
with good cardiac function.
consultation was to plan optimal neonatal management
and surgery, as the patient lived 250 km from our center.
At targeted fetal echocardiography, utilizing 2D and
color Doppler, there was normal abdominal and thoracic
situs, but ccTGA was evident (as in the description
of Case 1). Targeted examination with color Doppler
revealed an additional small (2 mm) subpulmonic VSD.
The pulmonary trunk had a smaller caliber than the
aorta (3.4 vs. 4.1 mm), suggesting possible pulmonary
stenosis, but peak velocity across the pulmonary valve
was 105 cm/s, within the normal range, with no turbulent
flow. No arrhythmia was documented during the course
of the pregnancy. There was persistence of the right
umbilical vein, coursing to the right of the gallbladder
towards the normally developed ductus venosus and
portal system. The patient was counseled as for a
compensated cardiac malformation with no necessity for
a switch operation after birth. A repeat ultrasound scan at
25 weeks confirmed the findings of ccTGA with VSD, but
demonstrated absence of a pressure gradient across the
pulmonary valve. Accidental preterm home birth occurred
at 31 weeks (a male infant weighing 1660 g), and the
infant was subsequently admitted to the neonatal intensive
care unit at the local hospital. The neonatal course was
uneventful, with cardiac compensation, and the child
was discharged 6 weeks later, weighing 2540 g. Postnatal
echocardiography confirmed the prenatal diagnosis of
ccTGA, with a 4-mm VSD. The great vessels were of
normal size and normal pressure. Echocardiography at
age 4 months demonstrated subvalvular and valvular
pulmonary stenosis with a pressure gradient of 64 mmHg,
in addition to the ccTGA and VSD. The child is
now developing normally at 3 years of age, and
echocardiography and ECG are stable, with no evidence
of arrhythmia or signs of cardiac decompensation.
Case 3
Fetal echocardiography at 23 weeks’ gestation incidentally revealed ccTGA, with normal abdominal and thoracic situs, in a 17-year-old patient who was a volunteer
at an obstetric ultrasound course. No additional heart
defects or arrhythmia were detected. The karyotype was
that of a normal male, with no 22q11.2 deletion. A male
infant (3060 g) was delivered spontaneously at 38 weeks.
Postnatally, intravenous prostaglandin was initiated, due
to the ‘TGA’ diagnosis, but was discontinued when
echocardiography confirmed ccTGA. Additionally, there
was a bicuspid aortic valve with normal velocities across
the valve. The child had a satisfactory neonatal course and
was discharged at 3 days. He is now 1 year old with no
arrhythmia or additional cardiac findings demonstrated
on the most recent echocardiography and ECG.
Case 2
DISCUSSION
A 21-year-old patient was referred at 20 weeks for a
second opinion scan after the diagnosis of complete
TGA was made at screening ultrasound. The aim of the
ccTGA is an uncommon congenital cardiac anomaly,
characterized by atrioventricular and ventriculoarterial
discordance1 . In this condition, with solitus (normal)
Copyright  2003 ISUOG. Published by John Wiley & Sons, Ltd.
Ultrasound Obstet Gynecol 2004; 23: 68–72.
70
McEwing and Chaoui
Figure 2 Sonographic appearances of complete transposition of the great arteries. In atrioventricular concordance the tricuspid valve
attaches lower within the ventricle, there is a moderator band on the right side and the lumen of the right ventricle is shorter than the left.
The great vessels arise in a parallel course and the aorta lies to the right and anterior of the pulmonary artery. AO, aorta; MV, mitral valve;
RA, LA, right and left atria; RV, LV, right and left ventricles; TP, pulmonary trunk; TV, tricuspid valve.
atrial arrangement, the systemic veins drain into
the morphologic right atrium, which is connected
to the morphologic left ventricle by a mitral valve.
The pulmonary artery is discordantly connected and
transposed, arising from the left ventricle. The left atrium,
receiving the pulmonary veins, joins the morphologic
right ventricle via a tricuspid valve and the transposed
aorta arises from the right ventricle. The aorta is located
anteriorly and to the left of the pulmonary trunk
(Figure 6). Transposition of the great vessels theoretically
corrects for the hemodynamic effects of the ventricular
inversion. However, associated cardiac anomalies are
common, and include cardiac malpositioning and situs
inversus, tricuspid valve dysplasia or atresia, double
outlet ventricle, VSD (present in over 50% of cases
and usually large and perimembranous) and pulmonary
outflow tract obstruction (in about 50% of cases, and
frequently associated with a large VSD)1 – 6 . Abnormal
atrioventricular conduction tissue frequently causes
conduction disturbances and predisposes to spontaneous
heart block1 – 6 . The estimated prevalence is less than
1% of live births with congenital heart disease;
but this estimate may be misleading as in utero
deaths from associated severe anomalies, particularly
tricuspid valve dysplasia or displacement, are not
uncommon1 – 3,5 .
Copyright  2003 ISUOG. Published by John Wiley & Sons, Ltd.
Embryologically, the condition is believed to be due
to abnormal left-looping (l-ventricular looping) of the
primitive cardiac tube, connected at one end to the
sinus venosus and at the other to the truncus arteriosus.
The morphologic right ventricle becomes left-sided,
the morphologic left ventricle becomes relatively rightsided, and the interventricular septum may become
more horizontally aligned, due to relative supero-inferior
positioning of the ventricles. The conotruncal septum
fails to rotate in the usual spiral fashion, leading to a
parallel arrangement of the outflow tracts. The mitral
and pulmonary valves are in fibrous continuity, while
the tricuspid valve is separated from the aortic valve
by a complete right ventricular infundibulum. The aorta
frequently lies anteriorly and to the left of the pulmonary
trunk1 – 3 .
In the absence of associated anomalies, patients may
be initially asymptomatic, with presentation not uncommonly in adult life with conduction disturbance, atrioventricular valve regurgitation or impairment of systemic
ventricular function and congestive heart failure5,6 . With
associated cardiac anomalies, presentation in the neonatal
period with bradycardia from atrioventricular block or
congestive heart failure is common, the latter often
attributable to associated VSD, tricuspid valve dysplasia or displacement or aortic arch obstruction1,2 . A major
Ultrasound Obstet Gynecol 2004; 23: 68–72.
Prenatal diagnosis of corrected transposition
71
Figure 3 Sonographic appearances of corrected transposition of the
great arteries. In atrioventricular discordance the right ventricle lies
on the left side and vice versa. The tricuspid valve is thus on the left
side, attaching lower within the ventricle, there is a moderator band
on the left side and the lumen on the left side is shorter than the
right. MV, mitral valve; RA, LA, right and left atria; RV, LV, right
and left ventricles; TV, tricuspid valve.
LV
LA
RA
RV
LA
RA
LV
RV
Normal
(AV-concordance)
Figure 5 Attachment of the papillary muscles in corrected
transposition of the great arteries. The vertical arrow points to the
attachment of the papillary muscles on the free wall and therefore it
is a mitral valve and the ventricle is the left ventricle. The
horizontal arrows point to the papillary attachment at the septum
and the apex, evidence of a tricuspid valve and an anatomically
right ventricle. RA, LA, right and left atria; RV, LV, right and left
ventricles.
Corrected TGA
(AV-discordance)
Figure 4 Attachment of the papillary muscles differs for the
tricuspid and mitral valves. The mitral valve papillary muscles
(black arrow) attach to the free wall and the tricuspid valve
papillary muscles (arrow head) attach to the heart apex and septum
as demonstrated in the left image demonstrating atrioventricular
concordance (the moderator band at the apex of the right ventricle
is indicated by a white arrow). In atrioventricular discordance, the
mitral valve is on the right side, the papillary muscles attach to the
free wall, and the tricuspid valve papillary muscles attach to the
apex on the left (compare with Figure 5). AV, atrioventricular; RA,
LA, right and left atria; RV, LV, right and left ventricles; TGA,
transposition of the great arteries.
concern in long-term follow-up in patients with ccTGA
is, however, the unpredictability of the right ventricle
to sustain systemic pressure. The development of tricuspid regurgitation is considered a risk factor and sign of
developing cardiac failure, which may lead to death or
necessitate cardiac transplantation5 .
Prenatal diagnosis is difficult and has been infrequently
reported. As far as we are aware, no reports exist
Copyright  2003 ISUOG. Published by John Wiley & Sons, Ltd.
in the literature to date of prenatal diagnosis of
isolated ccTGA. Associated anomalies, such as systemic
ventricular hypoplasia, severe aortic coarctation4 , situs
inversus7 , twisted atrioventricular connections8,9 and
complete heart block2 , have been described in the few
cases of ccTGA within the prenatal literature.
Fetal echocardiography should focus on identification
of the morphologic left and right ventricles. The fourchamber view allows assessment of typical ventricular
morphology; the morphologic right ventricle is characterized by a prominent moderator band, more apical
attachment of the atrioventricular valve, chordal attachment of the atrioventricular valve directly to the septum,
irregularity of the endocardial surface compared to the
smooth surface of the left ventricle and a more rounded or
triangular shape to the cavity compared to the more elongated appearance of the morphological left ventricle1,2 .
The papillary muscles of the morphological right ventricle
tend to attach distally and centrally, in contradistinction
to those of the morphological left ventricle, which attach
to the side wall of the ventricle. In congenitally corrected
transposition of the great vessels, the morphological right
ventricle lies posteriorly and to the left of the morphological left ventricle. There may be malalignment of the
interatrial septum relative to the interventricular septum1 .
Associated malformations may be evident on the fourchamber view; in particular VSD or Ebstein’s anomaly
Ultrasound Obstet Gynecol 2004; 23: 68–72.
McEwing and Chaoui
72
to hemodynamic changes occurring after birth, and the
possible development of heart block or right ventricular
dysfunction at any stage2 . With detection of additional
cardiac anomalies, the prognosis depends on the type of
associated abnormality.
In conclusion, the detection of parallel vessels on
prenatal ultrasound arising from two different chambers
is most likely to be complete transposition, but careful
examination of the chamber anatomy in the four-chamber
plane, in addition to assessment of the connection and
position of the great vessels (i.e. d- vs. l-malposition),
helps in the prenatal differentiation of ccTGA.
REFERENCES
Figure 6 Identification of a parallel course of the great vessels, with
the aorta anteriorly and to the left of the pulmonary trunk,
completes the diagnosis of corrected transposition of the great
arteries. AO, aorta; RV, LV, right and left ventricles; TP,
pulmonary trunk.
of the left atrioventricular valve should be excluded. The
outflow tracts should be carefully assessed; the two great
vessels characteristically arise with a parallel course. The
pulmonary outflow tract, arising from the morphological
left ventricle, is embedded between the two atrioventricular valves10 . Color Doppler facilitates assessment of the
course of the great vessels and associated anomalies such
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In prenatally diagnosed patients without associated
anomalies, a good mid-term prognosis may be expected,
but prediction of long-term prognosis can be difficult due
Copyright  2003 ISUOG. Published by John Wiley & Sons, Ltd.
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