What condition is characterized by reversal of the aorta and pulmonary artery?

• A. Coarctation of the aorta
• B. Transposition of the great vessels
• C. Tetralogy of Fallot
• D. Ventricular septal defect

Answer: (B)

Transposition of the great vessels is indicated by a reversal of the aorta and pulmonary artery. In this condition, the aorta arises from the right ventricle and the pulmonary artery from the left ventricle, creating two parallel circuits instead of one unified, series circulation. Because systemic and pulmonary blood are in parallel, oxygen-rich blood can’t adequately reach the body unless there’s mixing somewhere (for example via a patent foramen ovale/ASD, a VSD, or a PDA). Newborns typically become profoundly cyanotic soon after birth due to limited systemic oxygenation unless a shunt allows mixing. Acute management aims to keep the ductus arteriosus open with prostaglandin E1 to permit mixing, followed by definitive repair with an arterial switch operation in early infancy, which reassigns the great vessels so the aorta arises from the left ventricle and the pulmonary artery from the right ventricle. Other listed defects involve different anatomic problems (coarctation is narrowed aorta; tetralogy of Fallot includes VSD with overriding aorta and pulmonary stenosis; ventricular septal defect is a hole between ventricles) and do not describe the reversal of the great arteries.