What laboratory finding is expected in an infant with congenital heart disease and decreased pulmonary blood flow?

In infants with congenital heart disease that results in decreased pulmonary blood flow, polycythemia is a common laboratory finding. This occurs as a compensatory response to low oxygen levels (hypoxemia). When oxygen saturation in the blood is reduced due to inadequate blood flow to the lungs, the body senses the need for more oxygen-carrying capacity.

To address this, the kidneys produce increased amounts of erythropoietin (EPO), stimulating the bone marrow to produce more red blood cells. This leads to an increase in hemoglobin and hematocrit levels, resulting in polycythemia. Elevated red blood cell mass helps to enhance oxygen delivery to the tissues, compensating for the inadequate perfusion of the lungs.

The other options do not fit the clinical picture associated with decreased pulmonary blood flow in congenital heart defects. A decreased platelet count might be seen with other conditions but is not a typical finding related to decreased pulmonary blood flow. Decreased ferritin levels are usually indicative of iron deficiency, which is not directly related to the physiological responses seen in congenital heart diseases with low pulmonary blood flow. A shift to the left typically refers to a change in the white blood cell count in response to infection or inflammation, which is also not relevant