(See also Overview of Heart Defects.)
When the heart and blood vessels develop in the fetus, at first there is only one large tube, called the truncus, leaving the heart. Normally, the truncus divides into two blood vessels, the pulmonary artery and the aorta (see also Normal Fetal Circulation). Sometimes the truncus does not divide and persists during fetal development and after birth. There is one valve, the truncal valve, leading into this one artery, rather than separate aortic and pulmonic valves.
Persistent truncus arteriosus accounts for 1 to 2% of birth defects of the heart. Nearly all children with persistent truncus arteriosus also have a ventricular septal defect. Other problems that can be associated include a tight or leaky truncal valve, an interrupted aortic arch, a patent ductus arteriosus, an atrial septal defect, and DiGeorge syndrome.
Persistent Truncus Arteriosus
During the first few weeks of life, infants usually have mild cyanosis (bluish coloration of the skin) and symptoms and signs of heart failure (see figure Heart Failure: Pumping and Filling Problems), including shortness of breath, rapid breathing, poor feeding, and sweating.
Diagnosis is suspected based on findings during a doctor's examination of the newborn, including characteristic heart murmurs. A heart murmur is a sound created by turbulent blood flow through narrowed or leaking heart valves or through abnormal heart structures. Findings from chest x-rays and ECG, done when doctors suspect a heart defect, usually provide further clues to the diagnosis. Echocardiography (ultrasonography of the heart) confirms the diagnosis.
Cardiac catheterization, MRI, or CT is occasionally used to identify other coexisting heart problems before surgery.
Heart failure is treated with drugs to improve breathing until surgery can be done.
Surgery is usually done before the infant is 2 months old. Surgery consists of placement of a patch to repair the ventricular septal defect. Then doctors separate the pulmonary arteries from the truncus and attach them to the right ventricle using a tube (conduits). After this repair, the truncus functions as the aorta.
When a conduit is placed during early infancy, its size becomes inadequate as children grow, and additional surgery is needed to enlarge the conduit. Sometimes the child's own tissue can be used to construct the pathway from the right ventricle to the pulmonary arteries and, in that case, there is the potential for growth as the child grows.
Some children need to take antibiotics before visits to the dentist and before certain surgeries (such as on the respiratory tract). These antibiotics are used to prevent serious heart infections called endocarditis.