Transposition of the great arteries

The great vessels are reversed (transposed), with the aorta coming off the right ventricle and the pulmonary artery off the left ventricle. Affected children are therefore dependent on the ductus arteriosus (duct-dependent) to supply oxygenated blood to the systemic circulation. As the duct closes after birth, the baby will become profoundly cyanotic and acidotic. Chest X-ray shows a characteristic narrow mediastinum with an 'egg-on-side' appearance of the heart shadow. The switch operation is required as definitive management.