In a Down syndrome infant with a complete AV canal defect, which auscultatory finding is most consistent with pulmonary hypertension?

In a Down syndrome infant with a complete AV canal defect, which auscultatory finding is most consistent with pulmonary hypertension?

• A. Loud single S2
• B. Fixed split S2
• C. Hyperdynamic precordium
• D. Wide pulse pressure

Answer: (C)

When a Down syndrome infant has a complete AV canal defect, there is a large left-to-right shunt that causes increased pulmonary blood flow. Over time this can lead to pulmonary hypertension, which makes the heart work harder and often produces a high-output state. A hyperdynamic precordium—where the chest wall over the heart looks and feels unusually vigorous, with a strong, brisk impulse—reflects this increased cardiac output and rapid pulsations from the ventricle pumping against higher pressures in the pulmonary circulation. In the setting of pulmonary hypertension from a significant shunt, this exam finding can be the most striking and practical clue, signaling that the heart is operating at an elevated volume and pressure load. Other signs are less specific in this context. A loud single S2 can occur with pulmonary hypertension because the pulmonic component of S2 becomes pronounced, but in infants with substantial shunting the overall high-flow state often presents more prominently as a hyperdynamic precordium. A fixed split S2 points toward an atrial septal defect, not necessarily pulmonary hypertension specifically, and a wide pulse pressure is more typical of a large left-to-right shunt like a patent ductus arteriosus rather than isolated pulmonary hypertension.

When a Down syndrome infant has a complete AV canal defect, there is a large left-to-right shunt that causes increased pulmonary blood flow. Over time this can lead to pulmonary hypertension, which makes the heart work harder and often produces a high-output state. A hyperdynamic precordium—where the chest wall over the heart looks and feels unusually vigorous, with a strong, brisk impulse—reflects this increased cardiac output and rapid pulsations from the ventricle pumping against higher pressures in the pulmonary circulation. In the setting of pulmonary hypertension from a significant shunt, this exam finding can be the most striking and practical clue, signaling that the heart is operating at an elevated volume and pressure load.

Other signs are less specific in this context. A loud single S2 can occur with pulmonary hypertension because the pulmonic component of S2 becomes pronounced, but in infants with substantial shunting the overall high-flow state often presents more prominently as a hyperdynamic precordium. A fixed split S2 points toward an atrial septal defect, not necessarily pulmonary hypertension specifically, and a wide pulse pressure is more typical of a large left-to-right shunt like a patent ductus arteriosus rather than isolated pulmonary hypertension.