A.mother with diabetes gives birth to a baby who is diagnosed as having dextroposition
of the aorta and the pulmonary trunk with cyanosis and shortness of breath. Which of the
following structures is required to remain patent until surgical correction of the deformity?
(A) Umbilical arteries
(B) Umbilical vein
© Ductus arteriosus
(D) Ductus venosus
(E) Sinus venosus
The answer is C. A patent ductus arteriosus shunts blood from the pulmonary trunk to the
aorta, partially bypassing the lungs, and thus allowing mixed blood to reach the body tissues
and causing cyanosis. Dextroposition or transposition of the great arteries must be
accompanied by a VSD or a patent ductus arteriosus for the infant to survive. The transposition
causes oxygenated blood to pass from the left ventricle into the pulmonary trunk
and then into the lungs, but deoxygenated blood travels from the right ventricle into the
aorta and then into the systemic circulation.