A neonate presents with cyanosis that worsens with crying (paradoxically improves with feeding/crying). Echocardiography shows a single outlet vessel from the heart, with pulmonary arteries arising from the aorta. Failure of partitioning of which embryonic structure is responsible?

• A Truncus arteriosus (failure of aorticopulmonary septum formation) ✓
• B Bulbus cordis (failure of conus septum formation)
• C Sinus venosus (failure of septum secundum)
• D Common atrium (failure of septum primum)

Explanation

Persistent truncus arteriosus (PTA) results from failure of the aorticopulmonary septum (neural crest cell-derived) to divide the truncus arteriosus into the aorta and pulmonary trunk. This produces a single arterial trunk that gives rise to both systemic and pulmonary circulations. The condition is associated with DiGeorge syndrome (22q11 deletion). PTA presents with cyanosis and heart failure in neonates. The aorticopulmonary septum also contributes to the membranous ventricular septum; its absence also causes a subarterial VSD.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.