Truncus Arteriosus (TA)
 

Definition         What is truncus arteriosus?

In this heart defect the child is born with abnormal development of the blood vessels which emerge from the heart. Normally there are two arteries which carry blood from the heart to various parts of the body. The pulmonary artery carries blood from the right ventricle to the lungs and the aorta receives blood pumped from the left ventricle to deliver it to the body.

In this congenital heart disease there is a single vessel emerging from the heart, this is termed truncus arteriosus.  The truncus arteriosus then gives rise to the pulmonary arteries and aorta.

 

Only one great vessel arise from both ventricles (truncus arteriosus).  This single vessel then branches into a pulmonary artery and aorta.  In type I truncus arteriosus, such as in this diagram the pulmonary arteries arise as a single vessel from the truncus and then divides into two pulmonary arteries.

In truncus arteriosus type II, both pulmonary arteries emerge close to each other from the truncus and not as a single blood vessel as in type I.

In truncus arteriosus type III, the pulmonary arteries emerge apart from each other from the truncus and not as a single blood vessel as in type I, or close together as in type II.

In truncus arteriosus there is a hole between the two ventricles (ventricular septal defect or VSD) and there is only one blood vessel which emerges from both ventricles at the part where they communicate through the ventricular septal defect.
 

Incidence        How common or rare is this disease?

Represents 1% of children with heart diseases.   Occurs in 0.034-0.21 per 1,000 of live births.
 

Effects         What does it cause?

The hole between the two pumping chambers and the single artery (truncus arteriosus) coming out of the heart will cause the poorly oxygenated blood (blue in color) which is returning from the body and the well oxygenated blood (pink in color) which is returning from the lungs to mix together causing the blood going to the body to be somewhat blue resulting in bluish discoloration of the child (cyanosis). In addition there will be excessive blood flow to the lungs causing heart failure and eventually damage to the blood vessels of the lungs.

Blue blood from the right ventricle (de-oxygenated) and red blood from the left ventricle (oxygenated) mix together as they get into the truncus.  This results in blood going to the body which is less oxygenated than it should be and blood going to the lungs which is more oxygenated than it need to be.

 

Course         How would this disease progress?

Untreated, the child will initially suffer from heart failure, which manifest as rapid breathing, poor feeding and failure to gain weight and grow properly. Within months bluish discoloration of the skin will increase. As damage of the blood vessels of the lung progress this will result in less blood flow to the lungs which will eventually cause death. However, with surgical treatment children will lead practically normal lives.
 

Treatment         Does it require any treatment?

Surgical repair is recommended in the first two weeks of life. The surgeon separates the blood vessels going to the lungs (pulmonary arteries) from the truncus arteriosus and connect it to the right ventricle with a blood vessel (homograft) from a deceased child. In addition the hole in the heart (VSD) is closed with a patch such that the blood from the left ventricle pumps into the truncus arteriosus which now serve as the artery which provides blood to the body (aorta).

A conduit connects the RV to the pulmonary artery and the VSD is closed with a patch.

 

Complications

The blood vessels to the lung (pulmonary arteries) may be small to start with, in addition, surgical repair may require that the pulmonary arteries be stretched to be able to connect them to the right ventricle, these two factors may result in narrowing of the pulmonary arteries (branch pulmonary artery stenosis). To relief this, repeat surgery or widening the pulmonary arteries  in the cardiac catheterization laboratory may be needed.

Repeat surgery may also be needed to replace the homograft, since it stays fixed in size and does not grow with the child.