Definition of Truncus arteriosus:

Truncus arteriosus is a rare type of congenital heart disease characterized by a single blood vessel arising from the right and left ventricles, instead of the normal two (pulmonary artery and aorta).

There are four subtypes of truncus arteriosus, depending on the specific anatomy of the single vessel.

Causes, incidence, and risk factors:

In normal circulation, the pulmonary artery arises from the right ventricle, and the aorta arises from the left ventricle, which are separate from each other. Coronary arteries, which supply blood to the heart muscle, arise from the aorta, just above the valve at the entrance of the aorta.

In truncus arteriosus, a single arterial trunk arises from the ventricles. A large ventricular septal defect (hole between the two ventricles) is usually also present. As a result, the blue (unoxygenated) and red (oxygenated) blood mix completely.

Some of this mixed blood goes to the lungs, some to the coronary arteries, and the rest to the body. Usually, too much blood is sent to the lungs. Meanwhile, the blood going to the coronary arteries and the rest of the body often does not contain enough oxygen.

If left untreated, two problems occur. First, the lungs are filled with fluid, making it difficult to breathe. The second problem is that the blood vessels to the lungs become narrow and are permanently damaged. Over time, it becomes very hard for the heart to force blood to them. This is called pulmonary hypertension and it can be life-threatening.

Truncus arteriosus is very rare.