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KEY POINTS
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Key Points

  • 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.

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CONDITION
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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.

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In the original anatomic classification of Collett and Edwards (1949), four subtypes were described:

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Type I demonstrates a single pulmonary trunk arising from the truncus, which then subdivides into right and left pulmonary arteries.

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Type II demonstrates two pulmonary arteries arising directly from the posterior surface of the truncus.

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Type III demonstrates two pulmonary arteries arising from the lateral aspects of the truncus.

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Type IV demonstrates absent pulmonary arteries, but collateral arteries arising from the descending aorta supply the pulmonary vasculature.

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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:

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Type A1 demonstrates a partially separated pulmonary trunk.

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Type A2 demonstrates two pulmonary arteries arising directly from the truncus.

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Type A3 demonstrates a single pulmonary artery arising from the truncus together with further collaterals arising from the descending aorta.

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Type A4 demonstrates significant arch anomalies in association with the truncus.

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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).

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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 ...

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