Which auscultatory finding is most suggestive of an atrial septal defect?

Which auscultatory finding is most suggestive of an atrial septal defect?

• A. Fixed split S2
• B. Loud P2
• C. Single S2
• D. S4

Answer: (A)

Atrial septal defect creates a left-to-right shunt that increases right-sided blood flow, which delays the closure of the pulmonic valve. Because this delay is due to a chronic, volume-loaded right heart, the split between A2 and P2 remains constant regardless of breathing. That persistent, unchanging separation of the second heart sound is the hallmark finding and is most suggestive of an ASD. In contrast, a loud P2 points to elevated pulmonary pressures and could indicate pulmonary hypertension; a single S2 suggests loss of normal separation in certain conditions; and S4 reflects a stiff or noncompliant ventricle.

Atrial septal defect creates a left-to-right shunt that increases right-sided blood flow, which delays the closure of the pulmonic valve. Because this delay is due to a chronic, volume-loaded right heart, the split between A2 and P2 remains constant regardless of breathing. That persistent, unchanging separation of the second heart sound is the hallmark finding and is most suggestive of an ASD.

In contrast, a loud P2 points to elevated pulmonary pressures and could indicate pulmonary hypertension; a single S2 suggests loss of normal separation in certain conditions; and S4 reflects a stiff or noncompliant ventricle.