Truncus Arteriosus

Truncus Arteriosus

Truncus arteriosus is a single outlet from the heart arising from both ventricles with only one semilunar valve, and giving rise to both systemic and pulmonary circulation.

Incidence: 0.03-0.21 per 1000 births, accounting for 1% of structural heart defects.

Sonographic findings:

Fig 1, Fig 2, Fig 3, Fig 4

• One great vessel with a single semilunar valve that overrides the VSD.
• A direct continuity between one or two pulmonary arteries and the single arterial trunk.
• Normal aortic root excluding this condition.
• Abnormal truncal valve due to an abnormal number of cusps, thickening, stenosis, or insufficiency.
• Color Doppler imaging can aid in the identification of pulmonary trunk, arising from the main trunk, as well as the assessment of the degree of truncal valve dysfunction.
• Thymic hypoplasia or aplasia may be noted during echocardiography in the case of conotruncal defects related to deletion of chromosome 22q11.2.
• Pitfalls:
  • Tetralogy of Fallot with pulmonary atresia or pulmonary atresia with ventricular septal defect are often confused with truncus arteriosus.
  • The absence of the pulmonary outflow tract and failure to image the pulmonary artery makes it difficult to differentiate truncus arteriosus from pulmonary atresia with VSD.
• Usually diagnosed after 16-18 weeks.

Video clips of Truncus Arteriosus

Truncus arteriosus : Common trunk (aortic root) overiding both ventricles; small pulmonary artery (arrow) originating from the common trunk (*), (arrowhead =spine)

Truncus arteriosus:  Both pulmonary arteries arising from the enlarged common trunk