and the ventricular septal defect is closed with a patch. The pulmonary arteries are then detached from the common artery (truncus arteriosus) and connected to the right ventricle using a tube (a conduit or tunnel). The common artery, now separated from the pulmonary circulation, functions as the aorta with the truncal valve operating as the aortic valve. Most babies survive this surgical repair, but may require further surgery as they grow up. For example, the conduit does not grow with the child and may need to be replaced as the child grows. Furthermore, the truncal valve is often abnormal and may require future surgery to improve its function. There have been cases where the condition has been diagnosed at birth and surgical intervention is an option. A number of these cases have survived well into adulthood. Epidemiology Persistent truncus arteriosus is a rare cardiac abnormality that has a prevalence of less than 1%. Additional images See also Truncus arteriosus (embryology) Patent ductus arteriosus References External links A.D.A.M. Medical Encyclopedia from NCBI site. Truncus arteriosus Congenital heart defects Rare diseases