Which neonatal condition will cause mixing of oxygenated and deoxygenated blood?

• A. Atrial-septal defect
• B. Coarctation of the aorta
• C. Myelino-Madoff Syndrome
• D. Choanal Atresia

Answer: (A)

Mixing of oxygenated and deoxygenated blood happens when there’s an abnormal connection between the heart’s chambers, allowing blood to flow between areas with different oxygen content. An atrial septal defect creates a hole in the wall between the atria, so blood can move from the left atrium (high in oxygen) to the right atrium (venous blood). That left-to-right shunt mixes oxygen-rich blood with deoxygenated blood in the right heart and can alter how much blood, and how oxygenated, reaches the systemic circulation. In contrast, coarctation of the aorta is a narrowing of the aorta and doesn’t create interatrial mixing; choanal atresia is a nasal airway blockage affecting breathing, not blood mixing; and the other option describes a nonstandard condition that isn’t associated with mixing.