In an infant with trisomy 21 and a complete AV canal defect, which finding is expected?

In an infant with trisomy 21 and a complete AV canal defect, which finding is expected?

• A. Oxygen desaturation
• B. Hepatomegaly
• C. Crackles in both lungs
• D. Peripheral edema

Answer: (A)

A complete AV canal defect in a child with Down syndrome creates a large left-to-right shunt with significant pulmonary overcirculation. This puts the lungs under stress, leading to congestive heart failure in infancy. As the pulmonary vasculature becomes congested and gas exchange is impaired, the infant can develop hypoxemia, so oxygen saturation can drop. This makes desaturation a practical reflection of compromised oxygenation in the setting of substantial pulmonary involvement from the defect. Hepatomegaly, crackles, and peripheral edema are all common signs of heart failure in infants and reflect systemic venous congestion and pulmonary edema, but they don’t directly show the actual level of oxygen in the blood. The presence of desaturation points to the lungs not meeting the body’s oxygen needs, which is a key clinical cue in sizable AV canal lesions with pulmonary overcirculation and evolving pulmonary vascular changes.

A complete AV canal defect in a child with Down syndrome creates a large left-to-right shunt with significant pulmonary overcirculation. This puts the lungs under stress, leading to congestive heart failure in infancy. As the pulmonary vasculature becomes congested and gas exchange is impaired, the infant can develop hypoxemia, so oxygen saturation can drop. This makes desaturation a practical reflection of compromised oxygenation in the setting of substantial pulmonary involvement from the defect.

Hepatomegaly, crackles, and peripheral edema are all common signs of heart failure in infants and reflect systemic venous congestion and pulmonary edema, but they don’t directly show the actual level of oxygen in the blood. The presence of desaturation points to the lungs not meeting the body’s oxygen needs, which is a key clinical cue in sizable AV canal lesions with pulmonary overcirculation and evolving pulmonary vascular changes.