Persistent truncus arteriosus (PTA), often referred to simply as truncus arteriosus, is a rare form of congenital heart disease that presents at birth. In this condition, the embryological structure known as the truncus arteriosus fails to properly divide into the pulmonary trunk and aorta. This results in one arterial trunk arising from the heart and providing mixed blood to the coronary arteries, pulmonary arteries, and systemic circulation. For the International Classification of Diseases (ICD-11), the International Paediatric and Congenital Cardiac Code (IPCCC) was developed to standardize the nomenclature of congenital heart disease. Under this system, English is now the official language, and persistent truncus arteriosus should properly be termed common arterial trunk. Causes Most of the time, this defect occurs spontaneously. Genetic disorders and teratogens (viruses, metabolic imbalance, and industrial or pharmacological agents) have been associated as possible causes. Up to 50% (varies in studies) of cases are associated with chromosome 22q11 deletions (DiGeorge Syndrome). The neural crest, specifically a population known as the cardiac neural crest, directly contributes to the aorticopulmonary septum. Microablation of the cardiac neural crest in developing chick embryos and genetic anomalies affecting this population of cells in rodents results in persistent truncus arteriosus. Numerous perturbations affecting the cardiac neural crest have been associated with persistent truncus arteriosus, some of which include growth factors (fibroblast growth factor 8 and bone morphogenetic protein), transcription factors (T-box, Pax, Nkx2-5, GATA-6, and Forkhead), and gap junction proteins (Connexin). The cardiac neural crest also contributes the smooth muscle of the great arteries. Pathophysiology Anatomical changes associated with this disorder includes: single artery arising from the two ventricles which gives rise to both the aortic and pulmonary vessels abnormal truncal valve right sided aortic arch in about 30% of cases (not shown) large ventricular septal defect pulmonary hypertension complete mixing occurring at level of the great vessel right-to-left shunting of blood Diagnosis The diagnosis is based on: Cyanosis presents at birth Heart failure may occur within weeks Systolic ejection murmur is heard at the left sternal border Widened pulse pressure Bounding arterial pulses Loud second heart sound Biventricular hypertrophy Cardiomegaly Increased pulmonary vascularity Hypocalcemia (if associated with DiGeorge syndrome) Classification A well-known classification is the fourfold system developed by Collett and Edwards in 1949. Collett/Edwards Types I, II, and III are distinguished by the branching pattern of the pulmonary arteries: Type I: The branch pulmonary arteries arise from a single "main