Transposition of the great arteries
In
transposition of the great arteries, the aorta comes off the right ventricle and
the pulmonary artery arises from the left ventricle. The aorta will then take
unoxygenated blood back to the body before it can flow to the lungs for oxygen.
The pulmonary artery takes blood from the left side of the heart back to the
lungs. Infants born with transposition of the great arteries will be blue or
"cyanotic" at birth or soon after birth because unoxygenated blood is being
delivered to the body.
Before birth,
the normal fetus has a hole in the wall between the atria, the upper two
chambers of the heart. This opening is called a patent foramen ovale, or PFO.
There is also a vessel between the pulmonary artery and the aorta outside the
heart called a patent ductus arteriosus, or PDA. If the structures remain open
after the baby is born, blood will mix at these structures and some oxygenated
blood will get to the body. However, these structures are not meant to stay open
long after birth and will eventually close, allowing poorly oxygenated blood to
get to the body.
Treatment for transposition
of the great arteries
The surgery that is most commonly done
to repair this defect is the arterial switch or procedure. It is open-heart
surgery; the heart is stopped during the surgery. The aorta is cut above
the level of the coronary arteries, and the pulmonary artery is cut at the same
level. The coronary arteries are removed from the remaining base of the aorta
and then reattached to the base of the pulmonary artery. Then the aorta is sewn
to the base of the pulmonary artery and the pulmonary artery is sewn to the base
of the aorta, essentially "switching" the circulation and preserving the
coronary circulation. The aorta now comes off the left ventricle and can carry
the oxygenated blood to the body. The pulmonary artery comes off the right
ventricle, ready to carry the blood to the lungs for oxygen.