Truncus arteriosus is a rare type of heart disease that is present at birth (congenital) in which there is a single main blood vessel, rather than the normal two, carrying blood away from the heart. Instead of having a separate pulmonary artery, to carry blood to the lungs, and aorta, to carry blood to the rest of the body, a baby with truncus arteriosus has just one blood vessel leaving the heart which then branches into other blood vessels. Blood from both ventricles of the heart is mixed, resulting in a situation in which some oxygen-rich blood travels needlessly back to the lungs and some oxygen-poor blood travels to the rest of the body. Babies with this condition may have a bluish tint (cyanosis) to their skin, lips, and fingernails. In most cases, truncus arteriosus occurs in conjunction with a missing upper portion of the wall between the ventricles of the heart (ventricular septal defect).
Symptoms of truncus arteriosus include rapid breathing (tachypnea), lethargy, a bluish tint to the skin (cyanosis), poor feeding, difficulty breathing (dyspnea), and broadening of the fingertips (clubbing).
Other symptoms may include abnormal accumulations of fluid in the face, arms, and/or legs (edema), an abnormally rapid heartbeat, slow weight gain, failure to thrive, recurrent respiratory infections, poor physical development, and/or growth delays.
Congestive heart failure usually develops during the first few weeks of life because of the excessive amount of blood flow to the lungs. There may be abnormal enlargement of the heart (cardiomegaly), and/or the gradual development of obstructive lung disease.
When the blood pressure in the lungs is raised (pulmonary hypertension), the amount of work that the heart must perform is increased and blood vessels leading to and from the lungs become vulnerable to permanent damage.
The symptoms of truncus arteriosus are similar to those of a severe ventricular septal defect (VSD), a relatively common form of congenital heart disease. In VSD, the wall (septum) separating the two ventricles is incompletely formed before birth. This can result in inefficient distribution of oxygen to the various tissues of the body (hypoxia) and various degrees of congestive heart failure. Some infants with truncus arteriosus may also have narrowing or constriction (stenosis) of the valve that connects the heart and the major arteries. This may result in the backward flow of blood into the heart (regurgitation).
The exact cause of truncus arteriosus is not known. It has been suggested that some cases may develop due to the interaction of many genetic and environmental factors (multifactorial inheritance). The malformation is the result of an error in embryonic development. Approximately 35 percent of children with this disorder also have DiGeorge syndrome, which is a severe congenital immune deficiency disorder involving the thymus and parathyroid glands. (For more information on DiGeorge Syndrome, see the Related Disorders Section of this report.)
Truncus arteriosus is a rare, congenital heart defect that affects males and females in equal numbers. This disorder occurs in approximately 1 in 33,000 births in the United States. It is estimated that truncus arteriosus accounts for about 1 in 200 congenital heart defects.
Most commonly known risk factors are:
A mother who has had rubella (German measles) or other viral illnesses during early pregnancy.
A parent who had a congenital hearth defect
Excessive alcohol consumption during pregnancy
A mother who has diabetes
Taking medicines during pregnancy
The diagnosis of truncus arteriosus is confirmed by clinical evaluation, electrocardiogram (EKG), and specialized imaging techniques that allow the physician to view the structure of the heart. These may include an echocardiogram, angiocardiogram, and/or cardiac catheterization.
Babies with truncus arteriosus require corrective surgery if they are to thrive. In some cases, a preliminary surgical procedure may be performed (pulmonary artery banding) that is designed to ease the condition by reducing the pulmonary hypertension, but not to cure it.
Corrective surgery (open-heart surgery) will separate the pulmonary and aortic arteries, close the hole in the ventricle wall, and attach the pulmonary artery to the reinforced right ventricle wall.
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