Truncus arteriosus communis (TAC)

The truncus arteriosus communis (TAC) is a rare congenital heart malformation that accounts for only 0.5 - 0.8% of all heart defects. Its origin is based on a lack of ingrowth of the aortopulmonary septum: in this heart defect, only one artery emerges from the heart (conotruncal malformation).

Both the aorta and the pulmonary artery originate from this main trunk, the so-called ‘truncus’. The ‘truncus’ originates above a ventricular septal defect (VSD), which is always present in this heart defect. This ‘truncus’ then receives both oxygen-poor blood from the right ventricle and oxygen-rich blood from the left ventricle. This mixture of deoxygenated and oxygenated blood is then transported to both the body and the lungs. This heart defect can only be corrected by surgery. TAC is typically diagnosed prenatally by ultrasound and postnatally by echocardiography.

Initially, the newborns are relatively unremarkable, but after the pulmonary vascular resistance drops, the first clinical symptoms appear in the first few weeks of life. Typically, cardiac insufficiency (accelerated breathing, difficulty drinking and failure to thrive, susceptibility to infection) increases with advancing age. Correction is therefore targeted as early as the second to fourth week of life.

• Echocardiography
• Cardiac catheterisation only in exceptional cases
• Additional chromosome analysis if necessary

The operation

After opening the chest and starting the heart-lung machine, the heart is stopped using a cold infusion solution. The right ventricle is opened and the ventricular septal defect is closed above it. The two pulmonary arteries are then separated from the truncus and connected to the right ventricle with the help of an artificial vessel, a so-called conduit. The aorta is reconstructed with a patch.

The prognosis after the operation is good, but follow-up operations are necessary as the conduit does not grow and degenerates over the course of the patient's life and has to be replaced several times.

Possible complications in the long term

A conduit replacement is usually required within the first five years of the operation. The risk of such a routine repeat procedure is not very high.

Depending on the morphology of the truncal valve, additional stenoses or, much more frequently, insufficiencies may occur, making re-operation necessary.

The overall prognosis is good, endocarditis prophylaxis for the known indications is necessary.