11/14/24, 10\:40 AM Transposition of the Great Arteries (TGA)

Transposition of the Great Arteries (TGA)

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Transposition of the great arteries (TGA)\: congenital heart condition where the pulmonary trunk and aorta attachments
are swapped.
Prevalence\: accounts for 3% of all congenital heart disease and 20% of all cyanotic heart disease.
Aetiology\: aorta arises from the right ventricle and pulmonary artery from the left ventricle, resulting in two separate, non-
mixing circulations.
Survival\: depends on the presence of a shunt (patent ductus arteriosus, ventricular septal defect, or atrial septal defect) to
allow oxygenated blood to circulate.
Types\: Dextro-TGA (D-TGA) is the most common, requiring repair within the
repair without other defects.
Risk factors\: pregnancy-related health issues (alcoholism, smoking, rubella, diabetes), family history of congenital heart
disease; often associated with other cardiac conditions.
Neonatal presentation\: poor feeding, sweating during feeds, poor weight gain, tachypnoea, respiratory distress, cyanosis,
tachycardia, loud S2 heart sound, possible murmur.
Di
arteriosus.
Investigations\: antenatal ultrasound, pulse oximetry (hypoxia), ECG (initially normal, later right ventricular hypertrophy),
foetal ultrasound, chest X-ray (egg on a string), echocardiogram.
Medical management\: supplemental oxygen, prostaglandin E1 to maintain ductus arteriosus until surgery.
Surgical management\: balloon atrial septostomy to create an atrial septal defect for blood mixing, arterial switch
procedure within the
Complications\: without treatment, 90% die within the
disease, coronary artery disease; post-treatment complications include arrhythmias, pulmonary artery stenosis, coronary
artery stenosis, aortic regurgitation.
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Introduction

Transposition of the great arteries (TGA) is a congenital heart condition where the attachments of the pulmonary trunk and
the aorta to the heart are swapped (“transposed”).
TGA accounts for about 3% of all congenital heart disease and 20% of all cyanotic heart disease.

Aetiology

The aorta arises from the right ventricle, and the pulmonary artery arises from the left ventricle. This results in two separate
circulations that do not mix\: the left side of the heart travels through the pulmonary system, and the right side travels
through the systemic system.
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This does not cause a problem during pregnancy as gas and nutrient exchange occurs in the placenta, and blood does
not
Immediate survival is dependent on a shunt existing between the two separate circulations. This allows blood to become
oxygenated in the lungs as it
septal defect or atrial septal defect.
There are two types of TGA\:
Dextro transposition of the great arteries (D-TGA), also called complete TGA\: this is the most common form of TGA.
The aorta is found on the right of the pulmonary artery. Commonly, D-TGA needs to be repaired within a year of life.
Levo transposition of the great arteries (L-TGA), also called congenitally corrected transposition\: the aorta is found on
the left of the pulmonary artery. Without any other heart defects present, this may not need repair early in life.
Figure 1. Transposition of the great
arteries (D-TGA).
1

Risk factors

Risk factors for transposition of the great arteries include\:
Pregnancy-related health concerns (e.g. alcoholism, smoking, rubella and uncontrolled diabetes)
Family history of congenital heart disease
TGA is commonly accompanied by other cardiac conditions, including a ventricular septal defect, coarctation of the aorta
and pulmonary stenosis.

Clinical features

The clinical presentation of TGA occurs during the neonatal period, when the ductus arteriosus begins to close
physiologically (days 2-3).

History

In neonates, clinical features of TGA include\:
Poor feeding
Sweating during feeds
Poor weight gain
Tachypnoea and respiratory distress

Clinical examination

In a neonate, commonly, the only clinical sign of coarctation is weak femoral pulses. Other signs on clinical examination in
infancy include\:
Cyanosis
Tachycardia
Loud S2 heart sound
A murmur can be present depending on the shunt

Di

Di
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Tricuspid atresia (Ebstein’s anomaly)
Double-outlet right ventricle
Pulmonary atresia
Tetralogy of Fallot
Truncus arteriosus

Investigations

TGA is commonly diagnosed during pregnancy at antenatal ultrasound scans. This diagnosis requires close monitoring
during pregnancy, and arrangements regarding birth planning must be made so that the woman gives birth in a hospital
where the condition can be safely and appropriately managed after birth.

Bedside investigations

Relevant bedside investigations include\:
Pulse oximetry\: hypoxia suggesting possible cyanotic heart disease
ECG\: likely normal at

Imaging investigations

Relevant imaging investigations include\:
Foetal ultrasounds\: abnormal vessels within the heart may be identi
weeks gestation). A foetal echocardiogram may then be performed to con
Chest X-ray\: may see classic “egg on a string” appearance and increased vascular lung markings.
Echocardiogram\: determines the nature of the TGA to establish diagnosis and management options and identi
associated cardiac abnormalities.

Diagnosis

Early diagnosis is important because in TGA, blood
after birth, the ductus arteriosus closes; therefore, if left untreated, the condition worsens rapidly.

Management

If a shunt is present alongside TGA, it provides some time for de

Medical management

Supplemental oxygen may be required if oxygen saturations are low.
All deteriorating ductal-dependent lesions are treated with prostaglandin. Prostaglandin E1 is prescribed to maintain the
ductus arteriosus until surgery. This allows blood to

Surgical management

Following medical management, surgery is performed to close the ductus arteriosus and correct the coarctation.
Surgical options include balloon atrial septostomy to increase the mixing of the two circulatory systems and arterial
switch procedure.
Balloon atrial septostomy
Balloon septostomy involves inserting a catheter through the umbilicus into the foramen ovale and in
form a large atrial septal defect.
2
This means that blood on the left side of the heart returning from the lungs can
via the aorta to the body. After this, the patent ductus arteriosus is no longer required and so the prostaglandin infusion can
be stopped.
Arterial switch procedure
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The de
2
bypass machine within the
arteriosus can be corrected during this procedure.

Complications

Without treatment, 90% of infants will die within the
Complications of TGA include\:
Heart failure
Complete heart block
Valvular disease
Coronary artery disease
Complications can also occur after corrective treatment. These include\:
Arrhythmias
Pulmonary artery stenosis
Coronary artery stenosis
Aortic regurgitation

References

Centers for Disease Control and Prevention. License\: [Public domain]
Séguéla PE, Roubertie F, Kreitmann B, Mauriat P, Tafer N, Jalal Z, Thambo JB. Transposition of the great arteries\: Rationale
for tailored preoperative management. Arch Cardiovasc Dis. February 2017.

Reviewer

Dr Akmal Hussain
Consultant Paediatrician

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Contents

Introduction
Aetiology
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Risk factors
Clinical features
Di
Investigations
Diagnosis
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