Transposition of the great arteries is a congenital heart defect where the two main arteries that carry blood away from the heart - the pulmonary artery and the aorta - are switched. This results in deoxygenated blood being pumped to the body and oxygenated blood being pumped to the lungs. While transposition of the great arteries was first described centuries ago, no treatment was available until the 1950s with the development of surgical procedures. Today, survival rates following surgical repair exceed 90%.

2. Transposition of the great arteries (TGA) is the most common cyanotic
congenital heart lesion that presents in neonates. The hallmark of
transposition of the great arteries is ventriculoarterial discordance, in which
the aorta arises from the morphologic right ventricle and the pulmonary
artery arises from the morphologic left ventricle.
Although transposition of the great arteries was first described over 2
centuries ago, no treatment was available until the middle of the 20th
century, with the development of surgical atrial septectomy in the 1950s and
balloon atrial septostomy in the 1960s.
These palliative therapies were followed by physiological procedures (atrial
switch operation) and anatomic repair (arterial switch operation) (see the
video below). Today, the survival rate for infants with transposition of the
great arteries is greater than 90%.

6. Etiology
The etiology for transposition of the great arteries is unknown and is
presumed to be multifactorial.
The embryology likely involves abnormal persistence of the sub-aortic
conus with resorption or underdevelopment of the sub-pulmonary
conus (infundibulum). This abnormality aligns the aorta anterior and
superior with the right ventricle during development.

7. Symptoms :
Transposition of the great arteries symptoms include:
A. Blue color of the skin (cyanosis)
B. Shortness of breath
C. Lack of appetite
D. Poor weight gain
Risk factors:
Although the exact cause of transposition of the great arteries is unknown, several factors
may increase the risk of a baby being born with this condition, including:
a) A history of German measles (rubella) or another viral illness in the mother during
pregnancy
b) Poor nutrition during pregnancy
c) Drinking alcohol during pregnancy
d) A mother older than age 40
e) A mother who has poorly controlled diabetes
f) Down syndrome in the baby

9. The following are 3 common anatomic sites for mixing
of oxygenated and deoxygenated blood in
transposition of the great arteries:
Patent foramen ovale or atrial septal defect
Ventricular septal defect
Patent ductus arteriosus
One or all of these lesions can be present in concert
with dextro-transposition of the great arteries, and
the degree of arterial hypoxemia depends on the
degree of anatomic mixing.

10. Morbidity/mortality
The mortality rate in untreated patients is approximately 30% in the first week, 50% in the
first month, and 90% by the end of the first year. Long-term complications are secondary
to prolonged cyanosis and include polycythemia and hyper viscosity syndrome. These
patients may develop headache, decreased exercise tolerance, and stroke.
Thrombocytopenia is common in patients with cyanotic congenital heart disease leading
to bleeding complications. With improved diagnostic, medical, and surgical techniques,
the overall short-term and midterm survival rate exceeds 90%.
A small percentage (approximately 5%) of patients with transposition of the great arteries
(and often a ventricular septal defect) develop accelerated pulmonary vascular obstructive
disease and progressive cyanosis despite surgical repair or palliation. Long-term survival in
this subgroup is particularly poor.

12. Complications
Complications include the following:
 Congestive heart failure
 Arrhythmia
 Eisenmenger syndrome
(irreversible and progressive pulmonary vascular obstructive disease)
 Supra-valve pulmonary or branch pulmonary artery stenosis
 Coronary artery ostial obstruction (coronary ischemia)
Rare cases of supra-valvular aortic stenosis as a late complication of
transposition of the great arteries have been reported

14. Diagnosis
Although it's possible your baby's transposition of the great arteries may be diagnosed
before birth, it can be difficult to diagnose.
A physical exam alone isn't enough to accurately diagnose transposition of the great
arteries. One or more of the following tests are necessary for an accurate diagnosis:
i. Echocardiogram.
ii. Cardiac catheterization.
iii. Chest X-ray.
iv. Electrocardiogram.

15. Treatment
Medication: The medication prostaglandin E1 (alprostadil) helps keep the connection between the aorta and pulmonary
artery open (ductus arteriosus), increasing blood flow and improving mixing of oxygen-poor and oxygen-rich blood until
surgery can be performed.
Surgical options include:
i. Atrial septostomy procedure
ii. Arterial switch operation.
After corrective surgery, your baby will need lifelong follow-up care with a heart doctor (cardiologist) who specializes in
congenital heart disease to monitor his or her heart health. The cardiologist may recommend that your child avoid
certain activities, such as weightlifting, because they raise blood pressure and may stress the heart.
Pregnancy
If you had transposition of the great arteries repaired in your infancy, it's possible for you to have a healthy pregnancy,
but specialized care may be necessary. If you're thinking about becoming pregnant, talk to your cardiologist and
obstetrician before conceiving.
If you have complications, such as arrhythmias or serious heart muscle problems, pregnancy may pose risks to both you
and your fetus. In some situations, such as for women who have severe complications of their heart defect, pregnancy
isn't recommended even for those with a repaired transposition.