Truncus arteriosus communis (TAC)
In patients with a TAC only one vessel originates from the heart chambers. Generally the common vessel (truncus) overrides a ventricular septal defect. Depending on the origin of the pulmonary artery, different types are distinguished in the Van Praagh classification (A1-A4; B, without VSD, is rare):
- type A1-2 (most common types): the pulmonary artery stem arises as a singular vessel (type 1) or as separate pulmonary arteries (type 2, LPA,RPA) from the ascending aorta
- type A3: only one pulmonary artery arises from the ascending aorta, the others from the aortic arch, descending aorta or right ventricle (previously known as hemitruncus)
- type A4: truncus with aortic isthmus stenosis or interrupted aortic arch.
A median sternotomy is performed and the heart-lung machine connected to the patient. The right and left pulmonary arteries are temporarily occluded and the heart action is stopped by cardioplegia. After opening of the ascending aorta the pulmonary artery or arteries is/are cut out of the posterior wall of the aorta and the resulting defect is augmented with an autologous pericardial patch. The VSD is closed via the opened right ventricular outflow tract. A connection between the right ventricle and the pulmonary arteries is created directly or by means of a valve-bearing conduit.