Persistent truncus arteriosus
|Persistent Truncus Arteriosus|
|Classification and external resources|
Illustration of truncus arteriosus
Persistent truncus arteriosus (or Truncus arteriosus), also known as Common arterial trunk, 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.
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.
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.
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:
- 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
- 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
- Increased pulmonary vascularity
- Hypocalcemia (if associated with DiGeorge syndrome)
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). 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. 
- Barata, IA (Aug 2013). "Cardiac emergencies.". Emergency medicine clinics of North America 31 (3): 677–704. PMID 23915599.
- Collett RW, Edwards JE: Persistent truncus arteriosus: a classification according to anatomic types. Surg Clin North Am 1949; 29: 1245-70.
- "Persistent Truncus Arteriosus: Congenital Cardiovascular Anomalies: Merck Manual Professional". Retrieved 2007-11-04.
- "eMedicine - Truncus Arteriosus : Article by Doff McElhinney, MD". Retrieved 2007-11-04.
- Van Praagh R, Van Praagh S (1965). "The anatomy of common aorticopulmonary trunk (truncus arteriosus communis) and its embryologic implications. A study of 57 necropsy cases". Am. J. Cardiol. 16 (3): 406–25. doi:10.1016/0002-9149(65)90732-0. PMID 5828135.
- Kirby ML, Gale TF, and Stewart DE. (1983). "Neural crest cells contribute to normal aorticopulmonary septation.". Science 220 (4061): 1059–61. doi:10.1126/science.6844926. PMID 6844926.
- Jiang X, Rowitch DH, Soriano P, McMahon AP, Sucov HM.. (2000). "Fate of the mammalian cardiac neural crest...". Development (Cambridge, England) 127 (8): 1607–16. PMID 10725237.
- Hutson MR, Kirby ML.. (2003). "Neural crest and cardiovascular development: a 20-year perspective.". Birth Defects Res C Embryo Today. 69 (1): 2–13. doi:10.1002/bdrc.10002. PMID 12768653.
- Waller BR 3rd, McQuinn T, Phelps AL, Markwald RR, Lo CW, Thompson RP, Wessels A. (2000). "Conotruncal anomalies in the trisomy 16 mouse: an immunohistochemical analysis with emphasis on the involvement of the neural crest.". Anat. Rec. 260 (3): 279–93. doi:10.1002/1097-0185(20001101)260:3<279::AID-AR65>3.0.CO;2-2. PMID 11066038.
- Franz T. (1989). "Persistent truncus arteriosus in the Splotch mutant mouse.". Anat. Embryol. (Berlin). 180 (5): 457–64. doi:10.1007/BF00305120. PMID 2619088.
- Rodefeld M, Hanley F (2002). "Neonatal truncus arteriosus repair: surgical techniques and clinical management.". Semin Thorac Cardiovasc Surg Pediatr Card Surg Annu 5 (1): 212–7. doi:10.1053/pcsu.2002.31497. PMID 11994881.
- Parker, SE; Mai, CT; Canfield, MA; Rickard, R; Wang, Y; Meyer, RE; Anderson, P; Mason, CA; Collins, JS; Kirby, RS; Correa, A; National Birth Defects Prevention, Network (Dec 2010). "Updated National Birth Prevalence estimates for selected birth defects in the United States, 2004-2006.". Birth defects research. Part A, Clinical and molecular teratology 88 (12): 1008–16. PMID 20878909.
- Truncus Arteriosus Cincinnati Children's Medical Center
- A.D.A.M. Medical Encyclopedia from NCBI site.
- Surgery for Truncus Arteriosus: Powerpoint™ Presentation
- Truncus Arteriosus Repair in a Premature Newborn Baby
- Truncus arteriosus information for parents.