Understanding Transposition of the Great Arteries
• What is Transposition of the Great Arteries?
• How common is TGA and what causes it?
• How is TGA detected during pregnancy?
• How will my pregnancy be managed now that TGA has been diagnosed?
• How will the TGA be treated after birth?
• What is the long term outlook for babies with TGA?
• What are the chances I could have another baby with with TGA?
• What can I expect from the specialists at Morgan Stanley Children's Hospital?
WHAT IS TRANSPOSITION OF THE GREAT ARTERIES?
In the normal heart, the right side of the heart pumps blood
into the lungs where the blood can be filled with oxygen.
Blood returns from the lungs into the left side of the heart
and is then pumped into the body through the aorta.
In transposition of the great arteries (TGA) the outflow
tracts — the major blood vessels coming out of the right
and left sides of the heart — are reversed. Blood without
oxygen is pumped by the right side of the heart into the
body, and blood with oxygen is pumped by the left side of
the heart to the lungs.
Babies with TGA may not have enough oxygen going to the
body, which is referred to as 'cyanotic'. There are various
connections between the right and left sides of the heart
in fetal life that may help a baby be less cyanotic at birth.
Approximately 1/3 to 1/2 of babies with TGA also have a
ventricular septal defect. Although this defect will need
to be repaired, it will help the baby with oxygenation
HOW COMMON IS TGA AND WHAT CAUSES IT?
Transposition of the great arteries is seen in 2-4 out of every 10,000 live
births. It represents about 4 to 6% of all cases of heart defects present
at birth. It occurs equally in boys and girls.
No one knows for sure what causes TGA, but it likely happens very early in
pregnancy when the heart is developing, around 4 to 5 weeks gestation.
TGA is slightly more common in babies born to mothers with diabetes
mellitus, however, most cases are due to chance alone.
HOW IS TGA DETECTED DURING PREGNANCY?
TGA is usually detected during pregnancy through the sonogram
performed to check fetal development in the second trimester.
Thediagnosis is made by identifying the aorta coming out of the right
ventricle, and identifying the pulmonary artery coming out of the left
ventricle. (Normally the pulmonary artery should come out of the right
ventricle, and the aorta should come out of the left ventricle.) A ventricular septal defect may also be seen on this sonogram, although these may
be small and difficult to see. The diagnosis of TGA may also be made or
confirmed with a fetal echocardiogram. This is a specialized sonogram
of the fetal heart. At NewYork-Presbyterian Morgan Stanley Children's
Hospital/Columbia University Medical Center, all fetal echocardiograms
for TGA are performed by Pediatric Cardiologists with expertise in this
technique. Other cardiac defects can sometimes be seen in addition to
TGA. This sonogram will assess for any additional cardiac abnormalities.
Of cases of TGA diagnosed prenatally, essentially all are confirmed
HOW WILL MY PREGNANCY BE MANAGED NOW THAT TGA HAS BEEN DIAGNOSED?
An ultrasound will carefully examine the fetal development and assess
for any additional birth defects. Although TGA is only rarely associated
with additional abnormalities, it is important to investigate for other abnormalities
that my affect the baby's prognosis. Your prenatal care will
be managed by a Maternal-Fetal Medicine specialist, an obstetrician with
special training and expertise in high-risk pregnancies. A fetal echocardiogram
will be performed by a Pediatric Cardiologist to confirm the
diagnosis and exclude other heart problems. Over the course of your
pregnancy you will have additional ultrasounds to make sure that the
fetus is growing well.
As your delivery date approaches, induction of labor or a cesarean
section may be planned to optimize the delivery and ensure that the
medical specialists are available to care for the baby immediately after
birth. However, this may not be necessary in all cases, and labor management
does not need to be changed because your baby has TGA.
HOW WILL THE TGA BE TREATED AFTER BIRTH?
All patients with TGA require surgery. Typically surgery is performed
within the first week of life.
The arterial switch is most commonly performed to repair transposition.
In this surgery the great vessels (the main pulmonary artery and aorta)
are disconnected and reconnected to the correct ventricles (main pulmonary
artery to the right ventricle, and aorta to the left ventricle). The
coronary arteries, the blood vessels supplying the heart, must also be
transplanted to the left side of the heart.
A Rastelli operation is performed when transposition of the great arteries
is associated with a ventricular septal defect and subvalvular pulmonary
stenosis. The arterial switch cannot be performed for infants with these
defects, since it would result in aortic stenosis after surgery. In the
Rastelli operation, an intraventricular baffle is used to close the septal
defect and direct the pulmonary venous blood to the aorta. In addition,
a valved homograft conduit is placed to connect the right ventricle to the
WHAT IS THE LONG-TERM OUTLOOK FOR BABIES WITH TGA?
The operative mortality rate for the arterial switch procedure is reported
to be between 3 and 5%. Subsequent reoperation of catheterization
procedures may be required in up to 10% of patients. Importantly, long
term survival for patients with corrected TGA appears to be excellent.
Outcomes do seem to be much better after arterial switch than for the
There may be some late complications of the arterial switch procedure.
Patients with a corrected TGA should continue to be followed by
cardiologist throughout life. The most common late complications are
right ventricular dysfunction and tricuspid regurgitation. Other late
complications may include: supravalvular pulmonary stenosis, neoaortic
root enlargement, aortic regurgitation, left ventricular dysfunction,
branch pulmonary artery stenosis, aortic anastomotic stenosis, and
coronary artery stenosis or distortion.
WHAT ARE THE CHANCES I COULD HAVE ANOTHER BABY WITH TGA?
The chance for a second pregnancy affected by TGA is very low. When
one sibling is affected that risk is approximately 1.5%. Even when two
siblings are affected the risk is only 5% for another pregnancy.
TGA is very rarely associated with chromosomal abnormalities or
genetic syndromes. Speak to your genetic counselor about the options
for further testing.
WHAT CAN I EXPECT FROM THE SPECIALISTS AT MORGAN STANLEY CHILDREN'S HOSPITAL?
The specialists at Morgan Stanley Children's Hospital are among the
most experienced with TGA in the United States. The Center approach
includes a whole team in your prenatal care to optimize the chances
for your baby's well being after birth. You might expect to meet the
- Maternal-Fetal Medicine (MFM) — you will see one of a team of
MFMs, specialized obstetricians, throughout your pregnancy.
- Pediatric Cardiology — these doctors perform fetal echocardiograms
in the prenatal setting to diagnose TGA. The diagnosis will be
confirmed after birth, and these physicians will continue to follow
children with corrected TGA.
- Pediatric Cardiothoracic Surgery — these doctors perform the
surgery to correct TGA. A recently released report by the New York
State Department of Health has shown that NewYork-Presbyterian
Hospital is a leader in the state for best outcomes of surgeries
performed for children with congenital heart defects.
- Genetics — the genetic counselors will discuss the diagnosis of
TGA with you in more detail as well as recurrence risk and options for
- Neonatology — our top-ranked neonatology unit regularly cares for
children with congenital heart defects before and after surgery.