Signs and Symptoms of Transposition
Transposition of the great arteries can be diagnosed by a fetal ultrasound. This can be missed on a routine fetal ultrasound. Sometimes, a fetal echocardiogram done by specialists is needed to make a diagnosis of transposition in a fetus.
After birth, transposition is diagnosed in the first hours or days of life due to cyanosis or low oxygen levels. All babies have a patent ductus arteriosus (PDA) at birth that may allow enough mixing to prevent severe cyanosis. As the ductus arteriosus closes, as it will in the first hours or days of life, cyanosis gets more severe.
Rapid breathing is seen. This is due to the low oxygen levels in the blood. The infants do look uncomfortable breathing this fast.
A heart murmur heart murmur is often absent in the first days or weeks of life. If there is a site where blood mixing allows for safe oxygen levels, children will often develop signs and symptoms of congestive heart failure over the course of the first weeks or months of life.
Untreated, over 50 percent of infants with transposition will die in the first month of life. Ninety percent will die in the first year.
Diagnosing Transposition of the Great Arteries
When a newborn with significant cyanosis is first seen, they are often placed on supplemental oxygen. In cases of lung disease this often will improve the oxygen levels. With cardiac problems such as transposition there will be little effect on the child's oxygen levels. Failure of this "hyperoxia test" is often the first clue that a baby has a cardiac defect.
Echocardiography can quickly show the abnormal connections of the great arteries and other features of the cardiac anatomy. This includes the presence and size of an atrial or ventricular septal defect and the branching patterns of the coronary arteries.
If questions about the anatomy, such as the coronary artery pattern remain, cardiac catheterization or cardiac MRI may be done to get more details of the defect.
The immediate management of an infant with transposition focuses on getting safe oxygen levels. Stable cardiac and pulmonary function is important.
A continuous infusion of prostaglandin, a medication that will keep the ductus arteriosus open, is usually started when the diagnosis is suspected or confirmed. This will allow some mixing of oxygen-rich blood with oxygen-poor blood.
A procedure called a "balloon atrial septostomy" is often done once the diagnosis is confirmed. Before birth, all babies have a connection between the right atrium and the left atrium (called a foramen ovale). After birth, this normal connection may allow some mixing of blood. It may not provide enough mixing. The foramen ovale may be made bigger or stretched with a balloon, which will improve mixing. This balloon atrial septostomy procedure is done by passing a special balloon-tipped catheter into the heart from either a vessel in the umbilicus or a vessel in the groin. Often, the procedure is done at the bedside, with guidance from an echocardiogram. Occasionally, the procedure will be done in the catheterization laboratory.
A large atrial septal defect is created and allows excellent mixing of oxygen-rich and oxygen-poor blood. The body's oxygen saturation will stay in a safe range. After this procedure, the ductus arteriosus is no longer necessary. The prostaglandin infusion can be discontinued.
Babies can be stabilized for the short term. Surgical correction of the defect is always needed. In most cases, corrective surgery is done in the first week of life. In more complex cases, such as those with narrowing below the pulmonary valve (pulmonary stenosis), the time for surgery can vary.
In most cases of transposition, an arterial switch surgery is done. The arterial switch surgery involves cutting off the aorta and pulmonary arteries just above the point where they leave the heart. Part of this surgery is reconnecting them to the proper ventricle. The valve stays attached to the ventricle, so what was once the pulmonary valve is now the aortic valve. The aortic valve becomes the pulmonary valve.
Results of Treatment
Since the arterial switch surgery reconstructs the heart to a normal situation, long-term cardiac function should be excellent.
In a small percentage of children, narrowing (stenosis) may occur at the sites where the aorta and pulmonary artery are reattached. The narrowing may occur months or years following surgery. It may need additional treatment. Options for treating this narrowing include cardiac catheterization with balloon dilation of the narrowed area or another surgery.
Sometimes, the aorta becomes larger in its portion immediately after it arises from the left ventricle.
Rarely, there may be problems with flow through the coronary arteries.
Patients (after arterial switch surgery) usually have normal ventricular function and no heart rhythm abnormalities.
In later years, patients with the arterial switch surgery have good quality of life. They can do physical activity and sports without any difficulty or restrictions. Even though patients are expected to do well after the arterial switch surgery, long-term follow-up with the cardiologist is important.
Adult and Adolescent Management
All patients with transposition of the great arteries need to be followed by a congenital heart expert for life.
Learn more about the Adolescent and Adult Congenital Heart Disease Program.