Truncus arteriosus is a rare form of congenital cardiac disease in which a single cardiac outflow tract gives rise to the pulmonary, coronary, and systemic circulations.
Prenatal diagnosis relies upon failure to visualize three separate vessels in a transverse view through the upper mediastinum, and failure to visualize the normal branch pulmonary arteries and their origin from the right ventricle.
Up to 40% of cases are associated with a 22q11 deletion and the DiGeorge syndrome, thereby making amniocentesis a crucial part of the prenatal diagnostic evaluation.
While timing and mode of delivery do not need to be altered following the diagnosis, planned delivery in a tertiary care setting with appropriate pediatric cardiology backup is critical, as congestive cardiac failure can occur in the neonatal period.
Early definitive surgical repair is recommended, typically by means of a homograft from the right ventricle to the pulmonary artery, with closure of a VSD.
Long-term survival rates of 80% can be expected.
Truncus arteriosus (also known as common aorticopulmonary trunk, truncus arteriosus communis, and singleoutlet heart) refers to a single large ventricular outflow tract arising from both right and left ventricles. This single large outflow tract, or truncus, gives rise to the coronary arteries, aorta, and pulmonary arteries.
In the original anatomic classification of Collett and Edwards (1949), four subtypes were described:
Type I demonstrates a single pulmonary trunk arising from the truncus, which then subdivides into right and left pulmonary arteries.
Type II demonstrates two pulmonary arteries arising directly from the posterior surface of the truncus.
Type III demonstrates two pulmonary arteries arising from the lateral aspects of the truncus.
Type IV demonstrates absent pulmonary arteries, but collateral arteries arising from the descending aorta supply the pulmonary vasculature.
Van Praagh and Van Praagh (1965) subsequently described a different classification system in which type A truncus is associated with a ventricular septal defect (VSD) and type B truncus is not associated with a VSD. Type A truncus is divided further into four subtypes, which closely resemble the classification of Collett and Edwards:
Type A1 demonstrates a partially separated pulmonary trunk.
Type A2 demonstrates two pulmonary arteries arising directly from the truncus.
Type A3 demonstrates a single pulmonary artery arising from the truncus together with further collaterals arising from the descending aorta.
Type A4 demonstrates significant arch anomalies in association with the truncus.
Additionally, The Society of Thoracic Surgeons has further modified the classification by combining Types A1 and A2 from the Van Praagh and Van Praagh classification system (Jacobs, 2000).
Almost 60% of cases of truncus are type I, based on the classification of Collett and Edwards, 35% are type II, 5% are type III, and ...