What is truncus arteriosus?
Truncus arteriosus is a congenital (present at birth) defect that occurs due to abnormal development of the fetal heart during the first 8 weeks of pregnancy. The heart begins as a hollow tube, and the chambers, valves, and great arteries develop throughout the first 8 weeks of pregnancy. The aorta and pulmonary artery start as a single blood vessel, which eventually divides and becomes two separate arteries. Truncus arteriosus occurs when the single great vessel fails to separate completely, leaving a connection between the aorta and pulmonary artery.
Truncus arteriosis is a complex defect where there is a single (normally there are two separate arteries) vessel arising from the heart that forms the aorta and pulmonary artery. Another congenital heart defect that occurs with truncus arteriosus is a ventricular septal defect, where the upper portion of the wall between the left and right ventricles is missing. In rare cases, the ventricular septal defect is absent.
Truncus arteriosus occurs in less than one out of every 10,000 live births. It makes up 1 percent of all cases of congenital heart disease.
What are signs and symptoms of truncus arteriosus?
A baby with truncus arteriosus usually begins to have problems in the first week of life. Their oxygen levels are often slightly lower than normal resulting in cyanosis.
Because of the excessive amount of blood flow to the lungs with this anomaly, congestive heart failure (CHF) develops in the first week or two of life. On chest X-ray, the heart looks big and the lung fields look hazy indicating pulmonary overcirculation.
Signs of congestive heart failure are rapid breathing, shortness of breath, wheezing, grunting or very noisy breathing, nasal flaring, retractions, and restlessness.
The liver may be large due to a backup of blood or systemic congestion. Neck vein distention, poor feeding, and facial swelling are also seen.
Most often parents report rapid breathing, poor feeding, and a bluish color of the skin, especially around the mouth and nose. The signs and symptoms often increase when the infant eats.
What are treatment options for truncus arteriosus?
Initial treatment begins with stabilizing the infant. Medications to control congestive heart failure such as diuretics are often begun.
Ensuring good nutrition may require the use of a feeding tube or intravenous hyperalimentation. Surgery is usually performed after the infant is 2 weeks old, but before the blood vessels in the lungs are overwhelmed by extra blood flow and become diseased.
The surgical repair of truncus arteriosus requires the use of heart-lung bypass machine support. It involves three major components:
- Separating the pulmonary arteries from the main truncus (the truncus will remain as the first part of the aorta);
- closure of the ventricular septal defect using a patch
- creating a connection between the right ventricle and the pulmonary arteries using a valved conduit, usually a homograft pulmonary artery.
What are treatment results for truncus arteriosus?
Currently over 90 percent of children survive repair of truncus arteriosus. As the child grows, they will be followed by their cardiologist.
Typically, there will be no physical restrictions imposed on the child. As a child grows, the conduit that was used to connect the right ventricle and pulmonary arteries will not, and this will lead to obstruction to blood flow. The progression of this narrowing is easily followed by the cardiologist using physical examination and echocardiograms.
Recommendation for surgery to replace the right ventricle to pulmonary artery conduit with a larger one is usually made long before any symptoms would be evident.
This conduit will often need to be replaced two or three times during childhood to accommodate for growth. These operations are typically tolerated very well with a hospitalization of less than a week.
Problems with the truncal valve are more serious and can significantly affect the early and late mortality of these children. The more leaky (or narrowed) this valve is, the greater the chance that some intervention has to be done sooner than later (on average within 5 to 7 years) to prevent severe damage to the heart.
Source: University of Virginia Health System and Cinncinnati Childrens Hospital