Fixed splitting of the second heart sound is a classic finding in which congenital defect?

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Multiple Choice

Fixed splitting of the second heart sound is a classic finding in which congenital defect?

Fixed splitting of the second heart sound means the interval between A2 and P2 stays widened regardless of breathing. This is most classic for an atrial septal defect. The left-to-right shunt from ASD causes a constant increase in blood flow through the right heart and pulmonary circulation, which delays the closure of the pulmonic valve (P2) by a steady amount. Because this delay is ongoing, the A2–P2 interval remains wide and does not vary with inspiration or expiration, unlike normal physiology where inspiration lengthens the split. In contrast, the other defects don’t produce this pattern. Patent ductus arteriosus typically shows a continuous murmur and doesn't create a fixed A2–P2 interval. Ventricular septal defect and coarctation have different auscultatory findings and don’t characteristically cause fixed splitting of S2.

Fixed splitting of the second heart sound means the interval between A2 and P2 stays widened regardless of breathing. This is most classic for an atrial septal defect. The left-to-right shunt from ASD causes a constant increase in blood flow through the right heart and pulmonary circulation, which delays the closure of the pulmonic valve (P2) by a steady amount. Because this delay is ongoing, the A2–P2 interval remains wide and does not vary with inspiration or expiration, unlike normal physiology where inspiration lengthens the split.

In contrast, the other defects don’t produce this pattern. Patent ductus arteriosus typically shows a continuous murmur and doesn't create a fixed A2–P2 interval. Ventricular septal defect and coarctation have different auscultatory findings and don’t characteristically cause fixed splitting of S2.

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