Persistent truncus arteriosus
(or 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
never properly divides into the pulmonary artery
The most well-known classification was 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: truncus -> one pulmonary artery -> two lateral pulmonary arteries
- Type II: truncus -> two posterior/posterolateral pulmonary arteries
- Type III: truncus -> two lateral pulmonary arteries
The "Type IV" proposed in 1949 is no longer considered a form of PTA by most modern sources.
Another well-known classification was defined by Van Praaghs in 1965.
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. 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.
Anatomical changes associated with this disorder includes:
Treatment is with neonatal surgical repair. 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).